刺(ci)胞(bao)(bao)(bao)(bao)動(dong)物(wu)(wu)門(men)（Cnidaria）又稱(cheng)(cheng)刺(ci)細胞(bao)(bao)(bao)(bao)動(dong)物(wu)(wu)門(men)，過去稱(cheng)(cheng)為(wei)(wei)(wei)腔(qiang)(qiang)(qiang)腸動(dong)物(wu)(wu)門(men)（Coelenterata），因為(wei)(wei)(wei)它(ta)的含義(yi)適(shi)用(yong)于(yu)刺(ci)胞(bao)(bao)(bao)(bao)動(dong)物(wu)(wu)及櫛水(shui)(shui)母(mu)(mu)(mu)(mu)動(dong)物(wu)(wu)，所以現多已(yi)廢棄不(bu)用(yong)。刺(ci)胞(bao)(bao)(bao)(bao)動(dong)物(wu)(wu)體(ti)(ti)呈輻(fu)射或(huo)兩輻(fu)射對稱(cheng)(cheng)，僅具(ju)二胚(pei)層(ceng)(ceng)(ceng)，是(shi)(shi)最原(yuan)始的后(hou)生(sheng)(sheng)(sheng)動(dong)物(wu)(wu)。體(ti)(ti)壁由(you)外胚(pei)層(ceng)(ceng)(ceng)、內(nei)胚(pei)層(ceng)(ceng)(ceng)和(he)中膠層(ceng)(ceng)(ceng)組(zu)成(cheng)(cheng)。內(nei)胚(pei)層(ceng)(ceng)(ceng)圍(wei)成(cheng)(cheng)身體(ti)(ti)的整個(ge)內(nei)腔(qiang)(qiang)(qiang)稱(cheng)(cheng)消(xiao)化循環腔(qiang)(qiang)(qiang)，腔(qiang)(qiang)(qiang)腸一(yi)端為(wei)(wei)(wei)口，他端閉塞(sai)，無(wu)肛門(men)。體(ti)(ti)壁中有(you)(you)刺(ci)細胞(bao)(bao)(bao)(bao)。腔(qiang)(qiang)(qiang)腸動(dong)物(wu)(wu)的骨骼(ge)(ge)主要為(wei)(wei)(wei)外骨骼(ge)(ge)，具(ju)有(you)(you)支持和(he)保護功能。多由(you)幾丁質、角質和(he)石灰(hui)質構成(cheng)(cheng)。在很多珊瑚(hu)蟲(chong)(chong)中具(ju)有(you)(you)骨針或(huo)骨軸，它(ta)們存在于(yu)中膠層(ceng)(ceng)(ceng)，或(huo)突出于(yu)體(ti)(ti)表面。有(you)(you)無(wu)性(xing)和(he)有(you)(you)性(xing)兩種生(sheng)(sheng)(sheng)殖方(fang)式(shi)，并往(wang)往(wang)出現在同一(yi)種的生(sheng)(sheng)(sheng)活(huo)史(shi)中，即水(shui)(shui)螅(xi)型世(shi)代(dai)(dai)(dai)用(yong)無(wu)性(xing)出芽生(sheng)(sheng)(sheng)殖方(fang)式(shi)產(chan)(chan)生(sheng)(sheng)(sheng)水(shui)(shui)母(mu)(mu)(mu)(mu)型世(shi)代(dai)(dai)(dai)，而水(shui)(shui)母(mu)(mu)(mu)(mu)型個(ge)體(ti)(ti)脫(tuo)離母(mu)(mu)(mu)(mu)體(ti)(ti)，長大(da)成(cheng)(cheng)熟以后(hou)，又以有(you)(you)性(xing)生(sheng)(sheng)(sheng)殖方(fang)式(shi)產(chan)(chan)生(sheng)(sheng)(sheng)水(shui)(shui)螅(xi)型個(ge)體(ti)(ti)，兩個(ge)世(shi)代(dai)(dai)(dai)互(hu)相交替完成(cheng)(cheng)整個(ge)生(sheng)(sheng)(sheng)活(huo)史(shi)。約(yue)1萬種，可(ke)分(fen)為(wei)(wei)(wei)：水(shui)(shui)螅(xi)蟲(chong)(chong)綱(gang)、缽水(shui)(shui)母(mu)(mu)(mu)(mu)綱(gang)和(he)珊瑚(hu)蟲(chong)(chong)綱(gang)3綱(gang)，一(yi)般(ban)認為(wei)(wei)(wei)水(shui)(shui)螅(xi)蟲(chong)(chong)綱(gang)是(shi)(shi)最原(yuan)始的。絕(jue)大(da)部分(fen)海(hai)(hai)產(chan)(chan)，只(zhi)有(you)(you)少數(shu)(shu)種類(lei)(lei)(lei)產(chan)(chan)于(yu)淡水(shui)(shui)，以熱帶和(he)亞熱帶海(hai)(hai)洋的淺水(shui)(shui)區最豐富。較小種類(lei)(lei)(lei)可(ke)作魚類(lei)(lei)(lei)食餌，珊瑚(hu)骨骼(ge)(ge)（如紅珊瑚(hu)）可(ke)作工藝品，古珊瑚(hu)和(he)現代(dai)(dai)(dai)珊瑚(hu)可(ke)形成(cheng)(cheng)儲(chu)油層(ceng)(ceng)(ceng)，海(hai)(hai)邊的珊瑚(hu)礁可(ke)作天然海(hai)(hai)堤(di)；海(hai)(hai)蜇(zhe)鹽漬(zi)后(hou)成(cheng)(cheng)為(wei)(wei)(wei)食品，有(you)(you)些種類(lei)(lei)(lei)可(ke)作藥(yao)用(yong)；有(you)(you)些浮游(you)水(shui)(shui)母(mu)(mu)(mu)(mu)類(lei)(lei)(lei)可(ke)作為(wei)(wei)(wei)海(hai)(hai)流(liu)指示生(sheng)(sheng)(sheng)物(wu)(wu)；但是(shi)(shi)，有(you)(you)些大(da)型水(shui)(shui)母(mu)(mu)(mu)(mu)（如霞水(shui)(shui)母(mu)(mu)(mu)(mu)、根口水(shui)(shui)母(mu)(mu)(mu)(mu)）在大(da)量出現時，會阻(zu)塞(sai)或(huo)破壞(huai)漁網，有(you)(you)的海(hai)(hai)葵(kui)混于(yu)漁獲物(wu)(wu)中，人食后(hou)中毒致死。刺(ci)胞(bao)(bao)(bao)(bao)動(dong)物(wu)(wu)除極少數(shu)(shu)種類(lei)(lei)(lei)為(wei)(wei)(wei)淡水(shui)(shui)生(sheng)(sheng)(sheng)活(huo)外，絕(jue)大(da)多數(shu)(shu)種均(jun)為(wei)(wei)(wei)海(hai)(hai)洋生(sheng)(sheng)(sheng)活(huo)，多數(shu)(shu)在淺海(hai)(hai)，少數(shu)(shu)為(wei)(wei)(wei)深(shen)海(hai)(hai)種，現存約(yue)11000種，分(fen)為(wei)(wei)(wei)3個(ge)綱(gang)：水(shui)(shui)螅(xi)綱(gang)（Hydrozoa）、缽水(shui)(shui)母(mu)(mu)(mu)(mu)綱(gang)（Scyphozoa）、珊瑚(hu)綱(gang)（Anthozoa）。
刺胞動(dong)物很(hen)少能(neng)做(zuo)(zuo)主(zhu)動(dong)的(de)(de)移位運(yun)(yun)動(dong)，運(yun)(yun)動(dong)的(de)(de)能(neng)力是(shi)很(hen)有限的(de)(de)，特(te)別是(shi)水(shui)(shui)(shui)螅型。運(yun)(yun)動(dong)是(shi)由(you)表(biao)皮(pi)肌(ji)(ji)(ji)(ji)肉細胞中肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)所(suo)引起(qi)。例如水(shui)(shui)(shui)螅的(de)(de)身(shen)體(ti)可(ke)做(zuo)(zuo)伸(shen)縮(suo)(suo)(suo)運(yun)(yun)動(dong)，伸(shen)展(zhan)時(shi)(shi)體(ti)長可(ke)達15～20mm，收(shou)(shou)縮(suo)(suo)(suo)時(shi)(shi)體(ti)長僅0.5mm，這種(zhong)伸(shen)縮(suo)(suo)(suo)是(shi)爆(bao)發式的(de)(de)，每5～10分鐘左右爆(bao)發一(yi)次(ci)，主(zhu)要(yao)是(shi)由(you)外皮(pi)肌(ji)(ji)(ji)(ji)細胞的(de)(de)縱行肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)所(suo)引起(qi)。身(shen)體(ti)一(yi)側的(de)(de)肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)可(ke)引起(qi)身(shen)體(ti)的(de)(de)彎曲。有時(shi)(shi)靠彎曲身(shen)體(ti)及觸手(shou)并(bing)與基(ji)盤(pan)的(de)(de)交替附(fu)著而(er)做(zuo)(zuo)翻斛斗式的(de)(de)運(yun)(yun)動(dong)。基(ji)盤(pan)處粘細胞可(ke)分泌大量(liang)的(de)(de)氣(qi)泡，可(ke)使(shi)(shi)水(shui)(shui)(shui)螅在(zai)(zai)水(shui)(shui)(shui)面上做(zuo)(zuo)短暫的(de)(de)漂浮(fu)。缽(bo)水(shui)(shui)(shui)母(mu)(mu)(mu)類和珊(shan)瑚類的(de)(de)肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)已與表(biao)皮(pi)細胞分離(li)形(xing)成(cheng)獨立的(de)(de)一(yi)層(ceng)肌(ji)(ji)(ji)(ji)纖維(wei)(wei)，例如水(shui)(shui)(shui)母(mu)(mu)(mu)的(de)(de)肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)在(zai)(zai)下(xia)傘面及傘緣(yuan)形(xing)成(cheng)薄薄的(de)(de)一(yi)層(ceng)肌(ji)(ji)(ji)(ji)肉環，有的(de)(de)被輻管(guan)分離(li)成(cheng)片狀，其纖維(wei)(wei)有橫紋，它們做(zuo)(zuo)有規律的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)，使(shi)(shi)傘面有節奏的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)運(yun)(yun)動(dong)。當(dang)傘緣(yuan)收(shou)(shou)縮(suo)(suo)(suo)時(shi)(shi)，傘緣(yuan)內的(de)(de)水(shui)(shui)(shui)被噴出，由(you)于(yu)反作用力而(er)推動(dong)水(shui)(shui)(shui)母(mu)(mu)(mu)體(ti)向上運(yun)(yun)動(dong)，當(dang)傘及傘緣(yuan)肌(ji)(ji)(ji)(ji)肉舒張，被壓縮(suo)(suo)(suo)的(de)(de)中膠層(ceng)的(de)(de)彈性，使(shi)(shi)傘又恢(hui)復了原形(xing)，水(shui)(shui)(shui)又重新(xin)進(jin)入傘緣(yuan)內，身(shen)體(ti)下(xia)沉(chen)，但由(you)于(yu)收(shou)(shou)縮(suo)(suo)(suo)比舒張要(yao)快，所(suo)以(yi)水(shui)(shui)(shui)母(mu)(mu)(mu)還是(shi)可(ke)以(yi)向上垂直(zhi)運(yun)(yun)動(dong)。水(shui)(shui)(shui)母(mu)(mu)(mu)類的(de)(de)垂直(zhi)運(yun)(yun)動(dong)在(zai)(zai)有緣(yuan)膜的(de)(de)水(shui)(shui)(shui)母(mu)(mu)(mu)可(ke)以(yi)看的(de)(de)更為清楚。一(yi)旦肌(ji)(ji)(ji)(ji)肉停止收(shou)(shou)縮(suo)(suo)(suo)，水(shui)(shui)(shui)母(mu)(mu)(mu)就會自然(ran)下(xia)沉(chen)。其水(shui)(shui)(shui)平方向的(de)(de)運(yun)(yun)動(dong)多(duo)是(shi)被動(dong)的(de)(de)，多(duo)是(shi)由(you)于(yu)水(shui)(shui)(shui)流(liu)及風力所(suo)推動(dong)。又例如在(zai)(zai)珊(shan)瑚類，海(hai)葵的(de)(de)肌(ji)(ji)(ji)(ji)原纖維(wei)(wei)在(zai)(zai)隔膜上形(xing)成(cheng)發達的(de)(de)牽縮(suo)(suo)(suo)肌(ji)(ji)(ji)(ji)，它的(de)(de)收(shou)(shou)縮(suo)(suo)(suo)非常有力，所(suo)以(yi)當(dang)海(hai)葵固著在(zai)(zai)巖(yan)石上是(shi)很(hen)難將它取下(xia)的(de)(de)。
刺胞(bao)(bao)(bao)(bao)(bao)(bao)動物(wu)(wu)都是(shi)(shi)肉食(shi)(shi)(shi)性(xing)(xing)的(de)(de)(de)(de)(de)(de)，以(yi)浮游生物(wu)(wu)，小的(de)(de)(de)(de)(de)(de)甲(jia)殼(ke)類(lei)、多(duo)毛類(lei)甚至小的(de)(de)(de)(de)(de)(de)魚類(lei)為食(shi)(shi)(shi)。由(you)于(yu)食(shi)(shi)(shi)物(wu)(wu)的(de)(de)(de)(de)(de)(de)機械刺激和化學(xue)刺激，引(yin)起(qi)水螅類(lei)動物(wu)(wu)伸長觸(chu)手(shou)，并(bing)放出刺絲(si)囊(nang)以(yi)纏繞、麻痹、毒殺捕獲物(wu)(wu)，再(zai)將食(shi)(shi)(shi)物(wu)(wu)送(song)(song)入(ru)口中(zhong)(zhong)。口區腺細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)分泌(mi)的(de)(de)(de)(de)(de)(de)粘液有(you)(you)利(li)于(yu)食(shi)(shi)(shi)物(wu)(wu)的(de)(de)(de)(de)(de)(de)吞(tun)(tun)咽，食(shi)(shi)(shi)物(wu)(wu)進入(ru)胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)后(hou)，胃(wei)(wei)(wei)層的(de)(de)(de)(de)(de)(de)腺細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)開始(shi)分泌(mi)蛋白酶，分解、消化食(shi)(shi)(shi)物(wu)(wu)使之(zhi)形成(cheng)許多(duo)多(duo)肽，同(tong)時在胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)中(zhong)(zhong)由(you)于(yu)營(ying)(ying)養(yang)(yang)肌(ji)肉細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)(de)(de)鞭(bian)毛運動，食(shi)(shi)(shi)物(wu)(wu)得(de)以(yi)混合與推(tui)動。經這種細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)外消化之(zhi)后(hou)，開始(shi)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)內(nei)(nei)的(de)(de)(de)(de)(de)(de)消化過(guo)(guo)程(cheng)，營(ying)(ying)養(yang)(yang)肌(ji)肉細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)(de)(de)偽(wei)足(zu)吞(tun)(tun)噬(shi)食(shi)(shi)(shi)物(wu)(wu)顆粒，在細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)內(nei)(nei)形成(cheng)大量的(de)(de)(de)(de)(de)(de)食(shi)(shi)(shi)物(wu)(wu)泡，經過(guo)(guo)酸性(xing)(xing)及(ji)(ji)堿性(xing)(xing)的(de)(de)(de)(de)(de)(de)化學(xue)過(guo)(guo)程(cheng)之(zhi)后(hou)，營(ying)(ying)養(yang)(yang)物(wu)(wu)質由(you)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)(de)(de)擴散(san)作用輸送(song)(song)到全(quan)身。缽(bo)水母類(lei)及(ji)(ji)珊(shan)瑚(hu)(hu)類(lei)胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)結構比較復雜。缽(bo)水母的(de)(de)(de)(de)(de)(de)胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)中(zhong)(zhong)有(you)(you)各種輻管(guan)及(ji)(ji)環管(guan)，胃(wei)(wei)(wei)囊(nang)中(zhong)(zhong)有(you)(you)內(nei)(nei)胚層起(qi)源的(de)(de)(de)(de)(de)(de)胃(wei)(wei)(wei)絲(si)；珊(shan)瑚(hu)(hu)類(lei)的(de)(de)(de)(de)(de)(de)胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)被許多(duo)隔(ge)(ge)(ge)膜分隔(ge)(ge)(ge)成(cheng)許多(duo)小室(shi)，隔(ge)(ge)(ge)膜上有(you)(you)隔(ge)(ge)(ge)膜絲(si)。胃(wei)(wei)(wei)絲(si)及(ji)(ji)隔(ge)(ge)(ge)膜絲(si)中(zhong)(zhong)含有(you)(you)大量的(de)(de)(de)(de)(de)(de)刺細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)及(ji)(ji)腺細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)，它們(men)是(shi)(shi)將食(shi)(shi)(shi)物(wu)(wu)吞(tun)(tun)入(ru)胃(wei)(wei)(wei)腔(qiang)(qiang)(qiang)之(zhi)后(hou)才(cai)殺死(si)及(ji)(ji)消化。消化后(hou)的(de)(de)(de)(de)(de)(de)營(ying)(ying)養(yang)(yang)物(wu)(wu)通過(guo)(guo)各種管(guan)道輸送(song)(song)到全(quan)身，未消化的(de)(de)(de)(de)(de)(de)食(shi)(shi)(shi)物(wu)(wu)殘(can)渣仍由(you)口排出。糖元及(ji)(ji)脂肪(fang)是(shi)(shi)腔(qiang)(qiang)(qiang)腸(chang)動物(wu)(wu)的(de)(de)(de)(de)(de)(de)主要貯存(cun)物(wu)(wu)。刺胞(bao)(bao)(bao)(bao)(bao)(bao)動物(wu)(wu)中(zhong)(zhong)許多(duo)種類(lei)，特別是(shi)(shi)海(hai)洋中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)造礁珊(shan)瑚(hu)(hu)類(lei)，體內(nei)(nei)均有(you)(you)共生的(de)(de)(de)(de)(de)(de)藻(zao)類(lei)，如動物(wu)(wu)黃藻(zao)、腰(yao)鞭(bian)毛藻(zao)之(zhi)類(lei)。藻(zao)類(lei)能進行光合作用，產生甘油(you)、脂肪(fang)、糖及(ji)(ji)脯(fu)氨(an)酸等，并(bing)提供(gong)給(gei)刺胞(bao)(bao)(bao)(bao)(bao)(bao)動物(wu)(wu)作為其(qi)補充(chong)營(ying)(ying)養(yang)(yang)。這將在珊(shan)瑚(hu)(hu)綱中(zhong)(zhong)做進一步的(de)(de)(de)(de)(de)(de)敘述。
刺(ci)胞(bao)動物(wu)沒有專門的(de)(de)(de)(de)呼(hu)吸及排泄器官，由于身體(ti)是由兩層細胞(bao)圍(wei)繞(rao)胃循環腔(qiang)所組(zu)成，并(bing)通過口使(shi)胃腔(qiang)與(yu)外界(jie)相通，實際上體(ti)壁(bi)的(de)(de)(de)(de)兩層細胞(bao)均與(yu)外界(jie)環境(jing)接(jie)觸(chu)，所以呼(hu)吸與(yu)排泄作用(yong)可(ke)以由體(ti)壁(bi)細胞(bao)直接(jie)獨立進行。出、入口及胃腔(qiang)的(de)(de)(de)(de)水(shui)流可(ke)以攜帶入新鮮的(de)(de)(de)(de)氧氣，并(bing)帶走代謝產物(wu)。刺(ci)胞(bao)動物(wu)的(de)(de)(de)(de)主要含氮廢物(wu)是氨。
刺(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)是(shi)(shi)(shi)(shi)(shi)最早(zao)出(chu)現(xian)(xian)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)結(jie)(jie)(jie)構(gou)(gou)的(de)(de)(de)(de)多(duo)(duo)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)。神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)結(jie)(jie)(jie)構(gou)(gou)原始(shi)，是(shi)(shi)(shi)(shi)(shi)由(you)雙極(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)、多(duo)(duo)極(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)及(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)纖維(wei)聯(lian)合成(cheng)(cheng)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)叢或(huo)(huo)(huo)(huo)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)，一(yi)(yi)(yi)(yi)(yi)(yi)般位于(yu)(yu)外(wai)(wai)(wai)表皮(pi)(pi)(pi)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)基(ji)部(bu)肌(ji)肉(rou)(rou)層(ceng)之外(wai)(wai)(wai)，呈(cheng)網(wang)(wang)狀分(fen)布(bu)(bu)，故稱(cheng)(cheng)網(wang)(wang)狀神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)系(xi)統（netnervous system）。由(you)于(yu)(yu)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)(ke)向各個(ge)(ge)(ge)(ge)(ge)方(fang)向傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)，也(ye)(ye)稱(cheng)(cheng)為(wei)(wei)漫散(san)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)系(xi)統（diffusenervous system）。水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)就只(zhi)有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)，但大多(duo)(duo)數(shu)腔腸(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)除(chu)(chu)了(le)(le)表皮(pi)(pi)(pi)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)之外(wai)(wai)(wai)，在(zai)(zai)(zai)胃層(ceng)的(de)(de)(de)(de)基(ji)部(bu)也(ye)(ye)有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)，這兩(liang)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)或(huo)(huo)(huo)(huo)是(shi)(shi)(shi)(shi)(shi)完全(quan)獨(du)立(li)的(de)(de)(de)(de)，或(huo)(huo)(huo)(huo)有(you)(you)(you)(you)(you)(you)(you)(you)纖維(wei)相聯(lian)。1971年Westfall等(deng)首(shou)先證明(ming)(ming)(ming)了(le)(le)水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)及(ji)其他腔腸(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)在(zai)(zai)(zai)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)之間(jian)、神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)與(yu)(yu)效應器(qi)（表皮(pi)(pi)(pi)肌(ji)肉(rou)(rou)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)、刺(ci)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)、腺(xian)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)等(deng)）之間(jian)也(ye)(ye)存(cun)(cun)在(zai)(zai)(zai)著突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)傳(chuan)(chuan)(chuan)(chuan)遞(di)（synaptic transmission）。即(ji)(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)沖(chong)(chong)動(dong)(dong)(dong)(dong)的(de)(de)(de)(de)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)是(shi)(shi)(shi)(shi)(shi)由(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)的(de)(de)(de)(de)軸(zhou)突(tu)(tu)(tu)(tu)(tu)，傳(chuan)(chuan)(chuan)(chuan)遞(di)給另(ling)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)的(de)(de)(de)(de)樹(shu)突(tu)(tu)(tu)(tu)(tu)。軸(zhou)突(tu)(tu)(tu)(tu)(tu)的(de)(de)(de)(de)末(mo)(mo)(mo)端具(ju)有(you)(you)(you)(you)(you)(you)(you)(you)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)小泡(pao)（synaptic vesicle），樹(shu)突(tu)(tu)(tu)(tu)(tu)的(de)(de)(de)(de)末(mo)(mo)(mo)端沒(mei)有(you)(you)(you)(you)(you)(you)(you)(you)。傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)時(shi)(shi)(shi)(shi)，突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)小泡(pao)釋放(fang)乙(yi)酰膽(dan)堿引(yin)起(qi)(qi)后一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)的(de)(de)(de)(de)興(xing)奮，沖(chong)(chong)動(dong)(dong)(dong)(dong)傳(chuan)(chuan)(chuan)(chuan)出(chu)以后，乙(yi)酰膽(dan)堿被神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)末(mo)(mo)(mo)稍表面的(de)(de)(de)(de)膽(dan)堿酯酶水(shui)(shui)(shui)(shui)(shui)(shui)解成(cheng)(cheng)膽(dan)堿及(ji)乙(yi)酸而(er)解除(chu)(chu)了(le)(le)激(ji)活作(zuo)(zuo)用。以后又發(fa)現(xian)(xian)腔腸(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)分(fen)為(wei)(wei)兩(liang)種類(lei)型(xing)(xing)。一(yi)(yi)(yi)(yi)(yi)(yi)類(lei)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)是(shi)(shi)(shi)(shi)(shi)對(dui)稱(cheng)(cheng)性(xing)的(de)(de)(de)(de)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)（symmetrical），即(ji)(ji)兩(liang)個(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)(huo)多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)末(mo)(mo)(mo)端有(you)(you)(you)(you)(you)(you)(you)(you)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)小泡(pao)，因(yin)(yin)此沖(chong)(chong)動(dong)(dong)(dong)(dong)可(ke)(ke)以同(tong)時(shi)(shi)(shi)(shi)向兩(liang)個(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)(huo)幾(ji)個(ge)(ge)(ge)(ge)(ge)方(fang)向傳(chuan)(chuan)(chuan)(chuan)遞(di)，這種傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)也(ye)(ye)叫非(fei)(fei)極(ji)性(xing)的(de)(de)(de)(de)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)（nonpolarized transmission）；另(ling)一(yi)(yi)(yi)(yi)(yi)(yi)類(lei)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)是(shi)(shi)(shi)(shi)(shi)不對(dui)稱(cheng)(cheng)的(de)(de)(de)(de)（asymmetrical），即(ji)(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)只(zhi)有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)末(mo)(mo)(mo)端具(ju)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)小泡(pao)，神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)沖(chong)(chong)動(dong)(dong)(dong)(dong)只(zhi)能向一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)方(fang)向傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)，因(yin)(yin)此也(ye)(ye)稱(cheng)(cheng)為(wei)(wei)有(you)(you)(you)(you)(you)(you)(you)(you)極(ji)性(xing)的(de)(de)(de)(de)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)（polarized transmission）。最近的(de)(de)(de)(de)研究(jiu)證明(ming)(ming)(ming)刺(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)非(fei)(fei)極(ji)性(xing)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)是(shi)(shi)(shi)(shi)(shi)很(hen)普遍(bian)的(de)(de)(de)(de)。也(ye)(ye)有(you)(you)(you)(you)(you)(you)(you)(you)人認為(wei)(wei)刺(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)兩(liang)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)是(shi)(shi)(shi)(shi)(shi)由(you)多(duo)(duo)極(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)形成(cheng)(cheng)的(de)(de)(de)(de)非(fei)(fei)極(ji)性(xing)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)，也(ye)(ye)就是(shi)(shi)(shi)(shi)(shi)慢傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)系(xi)統；另(ling)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)是(shi)(shi)(shi)(shi)(shi)由(you)雙極(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)形成(cheng)(cheng)的(de)(de)(de)(de)極(ji)性(xing)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)，也(ye)(ye)就是(shi)(shi)(shi)(shi)(shi)快傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)系(xi)統。刺(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)可(ke)(ke)以有(you)(you)(you)(you)(you)(you)(you)(you)2個(ge)(ge)(ge)(ge)(ge)、3個(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)(huo)多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)長的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)突(tu)(tu)(tu)(tu)(tu)起(qi)(qi)，這些突(tu)(tu)(tu)(tu)(tu)起(qi)(qi)或(huo)(huo)(huo)(huo)與(yu)(yu)感(gan)(gan)(gan)官(guan)相聯(lian)、或(huo)(huo)(huo)(huo)與(yu)(yu)效應器(qi)相聯(lian)、或(huo)(huo)(huo)(huo)與(yu)(yu)其他神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)相聯(lian)、或(huo)(huo)(huo)(huo)者是(shi)(shi)(shi)(shi)(shi)同(tong)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)同(tong)時(shi)(shi)(shi)(shi)與(yu)(yu)感(gan)(gan)(gan)官(guan)與(yu)(yu)效應器(qi)相聯(lian)，這種多(duo)(duo)樣性(xing)說(shuo)明(ming)(ming)(ming)了(le)(le)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)的(de)(de)(de)(de)原始(shi)性(xing)。在(zai)(zai)(zai)生(sheng)理(li)意義上(shang)(shang)代(dai)表了(le)(le)高等(deng)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)所具(ju)有(you)(you)(you)(you)(you)(you)(you)(you)的(de)(de)(de)(de)感(gan)(gan)(gan)覺(jue)(jue)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)、運(yun)(yun)動(dong)(dong)(dong)(dong)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)及(ji)中(zhong)(zhong)樞神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)的(de)(de)(de)(de)起(qi)(qi)始(shi)階段。此外(wai)(wai)(wai)，刺(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)非(fei)(fei)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)，即(ji)(ji)上(shang)(shang)皮(pi)(pi)(pi)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)也(ye)(ye)是(shi)(shi)(shi)(shi)(shi)很(hen)常見的(de)(de)(de)(de)，例(li)如(ru)刺(ci)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)、表皮(pi)(pi)(pi)肌(ji)肉(rou)(rou)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)(ke)以完全(quan)獨(du)立(li)于(yu)(yu)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)而(er)被自(zi)身(shen)(shen)(shen)所控制(zhi)。水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)(xing)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)結(jie)(jie)(jie)構(gou)(gou)比水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)型(xing)(xing)復雜(za)(za)，例(li)如(ru)水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)，除(chu)(chu)了(le)(le)傘(san)(san)部(bu)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)網(wang)(wang)之外(wai)(wai)(wai)，傘(san)(san)緣(yuan)(yuan)的(de)(de)(de)(de)上(shang)(shang)皮(pi)(pi)(pi)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)分(fen)別在(zai)(zai)(zai)傘(san)(san)緣(yuan)(yuan)的(de)(de)(de)(de)上(shang)(shang)、下面集中(zhong)(zhong)形成(cheng)(cheng)兩(liang)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環。下面（或(huo)(huo)(huo)(huo)稱(cheng)(cheng)外(wai)(wai)(wai)面）的(de)(de)(de)(de)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環更(geng)發(fa)達。缽水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)的(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)(xing)多(duo)(duo)數(shu)沒(mei)有(you)(you)(you)(you)(you)(you)(you)(you)這種神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環，而(er)是(shi)(shi)(shi)(shi)(shi)在(zai)(zai)(zai)傘(san)(san)緣(yuan)(yuan)集中(zhong)(zhong)形成(cheng)(cheng)4～8個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)節(jie)(jie)(jie)。水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)(xing)個(ge)(ge)(ge)(ge)(ge)體均能表現(xian)(xian)出(chu)一(yi)(yi)(yi)(yi)(yi)(yi)種有(you)(you)(you)(you)(you)(you)(you)(you)節(jie)(jie)(jie)奏(zou)的(de)(de)(de)(de)收(shou)縮(suo)運(yun)(yun)動(dong)(dong)(dong)(dong)，這是(shi)(shi)(shi)(shi)(shi)由(you)于(yu)(yu)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)結(jie)(jie)(jie)構(gou)(gou)每隔一(yi)(yi)(yi)(yi)(yi)(yi)定時(shi)(shi)(shi)(shi)間(jian)能自(zi)發(fa)地產(chan)生(sheng)動(dong)(dong)(dong)(dong)作(zuo)(zuo)電位，并經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)過(guo)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)傳(chuan)(chuan)(chuan)(chuan)導(dao)(dao)(dao)(dao)(dao)引(yin)起(qi)(qi)整個(ge)(ge)(ge)(ge)(ge)身(shen)(shen)(shen)體的(de)(de)(de)(de)收(shou)縮(suo)。研究(jiu)已經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)證明(ming)(ming)(ming)這種自(zi)發(fa)的(de)(de)(de)(de)動(dong)(dong)(dong)(dong)作(zuo)(zuo)電位是(shi)(shi)(shi)(shi)(shi)由(you)起(qi)(qi)博(bo)(bo)點(dian)(dian)的(de)(de)(de)(de)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)所引(yin)起(qi)(qi)。起(qi)(qi)博(bo)(bo)點(dian)(dian)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)在(zai)(zai)(zai)水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)存(cun)(cun)在(zai)(zai)(zai)于(yu)(yu)外(wai)(wai)(wai)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環中(zhong)(zhong)，在(zai)(zai)(zai)缽水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)存(cun)(cun)在(zai)(zai)(zai)于(yu)(yu)感(gan)(gan)(gan)官(guan)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)節(jie)(jie)(jie)中(zhong)(zhong)。而(er)且每一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)節(jie)(jie)(jie)（一(yi)(yi)(yi)(yi)(yi)(yi)般4～8個(ge)(ge)(ge)(ge)(ge)）都(dou)有(you)(you)(you)(you)(you)(you)(you)(you)起(qi)(qi)博(bo)(bo)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)元(yuan)，它(ta)是(shi)(shi)(shi)(shi)(shi)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)有(you)(you)(you)(you)(you)(you)(you)(you)節(jie)(jie)(jie)奏(zou)博(bo)(bo)動(dong)(dong)(dong)(dong)的(de)(de)(de)(de)中(zhong)(zhong)心。一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)體似乎有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)起(qi)(qi)博(bo)(bo)點(dian)(dian)就足以引(yin)起(qi)(qi)身(shen)(shen)(shen)體有(you)(you)(you)(you)(you)(you)(you)(you)節(jie)(jie)(jie)奏(zou)的(de)(de)(de)(de)收(shou)縮(suo)運(yun)(yun)動(dong)(dong)(dong)(dong)，但實驗證明(ming)(ming)(ming)多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)起(qi)(qi)博(bo)(bo)點(dian)(dian)比僅有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)起(qi)(qi)博(bo)(bo)點(dian)(dian)能使(shi)收(shou)縮(suo)的(de)(de)(de)(de)節(jie)(jie)(jie)奏(zou)更(geng)有(you)(you)(you)(you)(you)(you)(you)(you)規律、更(geng)有(you)(you)(you)(you)(you)(you)(you)(you)保障(zhang)、使(shi)間(jian)隔的(de)(de)(de)(de)時(shi)(shi)(shi)(shi)間(jian)也(ye)(ye)較短。腔腸(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)型(xing)(xing)體沒(mei)有(you)(you)(you)(you)(you)(you)(you)(you)明(ming)(ming)(ming)顯的(de)(de)(de)(de)感(gan)(gan)(gan)官(guan)，其感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)(ke)分(fen)布(bu)(bu)全(quan)身(shen)(shen)(shen)，但觸(chu)(chu)(chu)手、口區較為(wei)(wei)豐富(fu)。水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)(xing)個(ge)(ge)(ge)(ge)(ge)體，在(zai)(zai)(zai)傘(san)(san)緣(yuan)(yuan)具(ju)有(you)(you)(you)(you)(you)(you)(you)(you)豐富(fu)的(de)(de)(de)(de)感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)或(huo)(huo)(huo)(huo)感(gan)(gan)(gan)覺(jue)(jue)器(qi)官(guan)。感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)體都(dou)是(shi)(shi)(shi)(shi)(shi)具(ju)纖毛(mao)的(de)(de)(de)(de)。感(gan)(gan)(gan)覺(jue)(jue)器(qi)官(guan)包括(kuo)眼(yan)點(dian)(dian)及(ji)平衡(heng)(heng)囊(nang)。眼(yan)點(dian)(dian)是(shi)(shi)(shi)(shi)(shi)由(you)感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)構(gou)(gou)成(cheng)(cheng)的(de)(de)(de)(de)杯狀物(wu)(wu)(wu)(wu)，內(nei)有(you)(you)(you)(you)(you)(you)(you)(you)色(se)素顆粒(li)分(fen)布(bu)(bu)，它(ta)對(dui)光(guang)線(xian)或(huo)(huo)(huo)(huo)有(you)(you)(you)(you)(you)(you)(you)(you)正(zheng)趨性(xing)，即(ji)(ji)有(you)(you)(you)(you)(you)(you)(you)(you)光(guang)時(shi)(shi)(shi)(shi)游向水(shui)(shui)(shui)(shui)(shui)(shui)面。或(huo)(huo)(huo)(huo)對(dui)光(guang)有(you)(you)(you)(you)(you)(you)(you)(you)負(fu)趨性(xing)，即(ji)(ji)有(you)(you)(you)(you)(you)(you)(you)(you)光(guang)時(shi)(shi)(shi)(shi)下沉水(shui)(shui)(shui)(shui)(shui)(shui)底，無光(guang)或(huo)(huo)(huo)(huo)弱光(guang)時(shi)(shi)(shi)(shi)浮向水(shui)(shui)(shui)(shui)(shui)(shui)面。平衡(heng)(heng)囊(nang)在(zai)(zai)(zai)水(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)結(jie)(jie)(jie)構(gou)(gou)簡單，在(zai)(zai)(zai)緣(yuan)(yuan)膜(mo)基(ji)部(bu)或(huo)(huo)(huo)(huo)下傘(san)(san)面神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環（即(ji)(ji)外(wai)(wai)(wai)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)環）處形成(cheng)(cheng)一(yi)(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)小囊(nang)，囊(nang)的(de)(de)(de)(de)內(nei)壁有(you)(you)(you)(you)(you)(you)(you)(you)感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)，細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)上(shang)(shang)也(ye)(ye)有(you)(you)(you)(you)(you)(you)(you)(you)纖毛(mao)。囊(nang)的(de)(de)(de)(de)底部(bu)有(you)(you)(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)(yi)鈣質結(jie)(jie)(jie)石。它(ta)是(shi)(shi)(shi)(shi)(shi)一(yi)(yi)(yi)(yi)(yi)(yi)種重力感(gan)(gan)(gan)受器(qi)。當傘(san)(san)緣(yuan)(yuan)傾(qing)斜時(shi)(shi)(shi)(shi)，結(jie)(jie)(jie)石與(yu)(yu)感(gan)(gan)(gan)覺(jue)(jue)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)纖毛(mao)接觸(chu)(chu)(chu)，并刺(ci)激(ji)纖毛(mao)細(xi)(xi)(xi)(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)以產(chan)生(sheng)動(dong)(dong)(dong)(dong)作(zuo)(zuo)電位，抑(yi)制(zhi)了(le)(le)該側肌(ji)肉(rou)(rou)纖維(wei)的(de)(de)(de)(de)收(shou)縮(suo)，通過(guo)肌(ji)肉(rou)(rou)收(shou)縮(suo)再調整身(shen)(shen)(shen)體使(shi)恢復平衡(heng)(heng)位置。缽水(shui)(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)的(de)(de)(de)(de)平衡(heng)(heng)囊(nang)結(jie)(jie)(jie)構(gou)(gou)更(geng)復雜(za)(za)，將在(zai)(zai)(zai)有(you)(you)(you)(you)(you)(you)(you)(you)關(guan)節(jie)(jie)(jie)中(zhong)(zhong)敘述
無性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)及(ji)(ji)有(you)性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)在(zai)(zai)腔(qiang)(qiang)腸(chang)動(dong)(dong)物(wu)(wu)中(zhong)都是(shi)(shi)很普遍的(de)(de)(de)(de)(de)(de)(de)。無性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)的(de)(de)(de)(de)(de)(de)(de)主要形(xing)式(shi)是(shi)(shi)出(chu)(chu)(chu)芽(ya)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)，特別(bie)是(shi)(shi)在(zai)(zai)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)更為(wei)(wei)常見。例(li)(li)如水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)出(chu)(chu)(chu)芽(ya)時從(cong)身體(ti)(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)(de)靠基(ji)部(bu)(bu)通(tong)過(guo)體(ti)(ti)(ti)(ti)壁及(ji)(ji)胃(wei)腔(qiang)(qiang)的(de)(de)(de)(de)(de)(de)(de)向外(wai)(wai)突出(chu)(chu)(chu)，再(zai)長出(chu)(chu)(chu)觸手與(yu)口即形(xing)成(cheng)(cheng)芽(ya)體(ti)(ti)(ti)(ti)，以后(hou)芽(ya)體(ti)(ti)(ti)(ti)與(yu)母(mu)體(ti)(ti)(ti)(ti)分(fen)離(li)即形(xing)成(cheng)(cheng)新的(de)(de)(de)(de)(de)(de)(de)個(ge)(ge)體(ti)(ti)(ti)(ti)。但(dan)(dan)在(zai)(zai)藪枝(zhi)螅(xi)(xi)(xi)（Obelia）所(suo)(suo)形(xing)成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)(de)芽(ya)體(ti)(ti)(ti)(ti)與(yu)母(mu)體(ti)(ti)(ti)(ti)不(bu)分(fen)離(li)則(ze)形(xing)成(cheng)(cheng)了群體(ti)(ti)(ti)(ti)。其(qi)次(ci)，也(ye)可以通(tong)過(guo)分(fen)裂(lie)(lie)方式(shi)進(jin)行無性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)，主要發生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)在(zai)(zai)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)，例(li)(li)如海葵可以縱分(fen)裂(lie)(lie)，缽(bo)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)母(mu)的(de)(de)(de)(de)(de)(de)(de)幼(you)體(ti)(ti)(ti)(ti)以橫分(fen)裂(lie)(lie)進(jin)行無性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)。此外(wai)(wai)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)一(yi)(yi)般(ban)具(ju)有(you)很強的(de)(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)能力，例(li)(li)如，將水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)切成(cheng)(cheng)數(shu)(shu)段，條件合宜時每段都可以再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)成(cheng)(cheng)一(yi)(yi)個(ge)(ge)新的(de)(de)(de)(de)(de)(de)(de)個(ge)(ge)體(ti)(ti)(ti)(ti)，再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)時口與(yu)反口端(duan)的(de)(de)(de)(de)(de)(de)(de)極(ji)性不(bu)變，但(dan)(dan)口端(duan)的(de)(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)速(su)(su)度(du)比反口端(duan)迅速(su)(su)。所(suo)(suo)以水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)的(de)(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)現(xian)象也(ye)被(bei)認為(wei)(wei)是(shi)(shi)無性生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)的(de)(de)(de)(de)(de)(de)(de)一(yi)(yi)種方式(shi)。有(you)些(xie)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)出(chu)(chu)(chu)現(xian)在(zai)(zai)多數(shu)(shu)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)及(ji)(ji)所(suo)(suo)有(you)的(de)(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)母(mu)型(xing)，除少數(shu)(shu)種類(lei)(lei)例(li)(li)如水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)為(wei)(wei)雌雄同體(ti)(ti)(ti)(ti)之外(wai)(wai)，絕大多數(shu)(shu)種類(lei)(lei)為(wei)(wei)雌雄異(yi)體(ti)(ti)(ti)(ti)（或異(yi)群體(ti)(ti)(ti)(ti)）。生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)細胞(bao)來(lai)源(yuan)于(yu)間細胞(bao)，然(ran)后(hou)遷移到固(gu)定(ding)的(de)(de)(de)(de)(de)(de)(de)位(wei)置上(shang)(shang)形(xing)成(cheng)(cheng)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)腺。水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)蟲(chong)(chong)綱(gang)的(de)(de)(de)(de)(de)(de)(de)動(dong)(dong)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)腺來(lai)源(yuan)于(yu)表皮層(ceng)(ceng)，例(li)(li)如水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)，水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)母(mu)的(de)(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)腺位(wei)于(yu)放(fang)射管下(xia)或垂唇(chun)周圍，但(dan)(dan)都是(shi)(shi)來(lai)源(yuan)于(yu)表皮層(ceng)(ceng)細胞(bao)。缽(bo)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)母(mu)綱(gang)的(de)(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)細胞(bao)起源(yuan)于(yu)胃(wei)層(ceng)(ceng)位(wei)于(yu)胃(wei)囊(nang)低(di)部(bu)(bu)。珊瑚綱(gang)的(de)(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)細胞(bao)是(shi)(shi)由胃(wei)腔(qiang)(qiang)中(zhong)的(de)(de)(de)(de)(de)(de)(de)隔膜上(shang)(shang)發生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)，也(ye)是(shi)(shi)內(nei)胚(pei)(pei)(pei)層(ceng)(ceng)來(lai)源(yuan)。腔(qiang)(qiang)腸(chang)動(dong)(dong)物(wu)(wu)只有(you)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)腺，沒(mei)有(you)出(chu)(chu)(chu)現(xian)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)導(dao)管及(ji)(ji)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)附(fu)屬腺，生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)細胞(bao)成(cheng)(cheng)熟之后(hou)由口排(pai)出(chu)(chu)(chu)，或由體(ti)(ti)(ti)(ti)壁破裂(lie)(lie)而(er)釋放(fang)。受精(jing)作用依不(bu)同的(de)(de)(de)(de)(de)(de)(de)種而(er)異(yi)，或在(zai)(zai)體(ti)(ti)(ti)(ti)外(wai)(wai)海水(shui)(shui)(shui)(shui)(shui)(shui)(shui)中(zhong)進(jin)行，或在(zai)(zai)垂管的(de)(de)(de)(de)(de)(de)(de)表面，或在(zai)(zai)胃(wei)腔(qiang)(qiang)內(nei)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)腺的(de)(de)(de)(de)(de)(de)(de)部(bu)(bu)位(wei)進(jin)行。卵(luan)(luan)裂(lie)(lie)是(shi)(shi)完全的(de)(de)(de)(de)(de)(de)(de)，形(xing)成(cheng)(cheng)中(zhong)空的(de)(de)(de)(de)(de)(de)(de)囊(nang)胚(pei)(pei)(pei)，經(jing)移入法或內(nei)陷(xian)法形(xing)成(cheng)(cheng)原(yuan)腸(chang)胚(pei)(pei)(pei)，結果(guo)形(xing)成(cheng)(cheng)兩層(ceng)(ceng)細胞(bao)，即兩個(ge)(ge)胚(pei)(pei)(pei)層(ceng)(ceng)，內(nei)部(bu)(bu)成(cheng)(cheng)團的(de)(de)(de)(de)(de)(de)(de)細胞(bao)為(wei)(wei)內(nei)胚(pei)(pei)(pei)層(ceng)(ceng)，將來(lai)形(xing)成(cheng)(cheng)成(cheng)(cheng)體(ti)(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)(de)胃(wei)層(ceng)(ceng)，外(wai)(wai)表的(de)(de)(de)(de)(de)(de)(de)一(yi)(yi)層(ceng)(ceng)為(wei)(wei)外(wai)(wai)胚(pei)(pei)(pei)層(ceng)(ceng)，將來(lai)形(xing)成(cheng)(cheng)成(cheng)(cheng)體(ti)(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)(de)表皮層(ceng)(ceng)。實心(xin)的(de)(de)(de)(de)(de)(de)(de)原(yuan)腸(chang)胚(pei)(pei)(pei)迅速(su)(su)延長，體(ti)(ti)(ti)(ti)表出(chu)(chu)(chu)現(xian)纖毛，形(xing)成(cheng)(cheng)了自(zi)由游泳的(de)(de)(de)(de)(de)(de)(de)浮浪幼(you)蟲(chong)(chong)（planula）。浮浪幼(you)蟲(chong)(chong)早期(qi)沒(mei)有(you)口及(ji)(ji)胃(wei)腔(qiang)(qiang)，游泳一(yi)(yi)段時間之后(hou)，固(gu)著在(zai)(zai)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)草、巖石或其(qi)他物(wu)(wu)體(ti)(ti)(ti)(ti)上(shang)(shang)發育成(cheng)(cheng)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)型(xing)體(ti)(ti)(ti)(ti)，或再(zai)經(jing)過(guo)出(chu)(chu)(chu)芽(ya)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)形(xing)成(cheng)(cheng)群體(ti)(ti)(ti)(ti)。淡水(shui)(shui)(shui)(shui)(shui)(shui)(shui)生(sheng)(sheng)(sheng)(sheng)(sheng)(sheng)活的(de)(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)(shui)(shui)螅(xi)(xi)(xi)沒(mei)有(you)幼(you)蟲(chong)(chong)期(qi)，其(qi)受精(jing)卵(luan)(luan)直接(jie)發育。
巧笑倩兮
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