芒果视频下载

基本介紹

刺(ci)胞(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)門(men)（Cnidaria）又稱(cheng)(cheng)刺(ci)細胞(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)門(men)，過去(qu)稱(cheng)(cheng)為(wei)(wei)(wei)(wei)腔(qiang)(qiang)(qiang)腸(chang)(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)門(men)（Coelenterata），因為(wei)(wei)(wei)(wei)它的(de)(de)(de)(de)含義適用于(yu)(yu)刺(ci)胞(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)及櫛(zhi)水(shui)(shui)(shui)(shui)母(mu)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)，所以(yi)現(xian)多(duo)已廢(fei)棄不用。刺(ci)胞(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)體(ti)(ti)呈(cheng)輻射或(huo)兩輻射對稱(cheng)(cheng)，僅具二(er)胚(pei)(pei)層(ceng)(ceng)(ceng)(ceng)，是(shi)最(zui)原(yuan)始的(de)(de)(de)(de)后(hou)生(sheng)(sheng)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)。體(ti)(ti)壁由(you)外(wai)胚(pei)(pei)層(ceng)(ceng)(ceng)(ceng)、內胚(pei)(pei)層(ceng)(ceng)(ceng)(ceng)和(he)(he)中(zhong)(zhong)膠層(ceng)(ceng)(ceng)(ceng)組成。內胚(pei)(pei)層(ceng)(ceng)(ceng)(ceng)圍(wei)成身體(ti)(ti)的(de)(de)(de)(de)整個(ge)內腔(qiang)(qiang)(qiang)稱(cheng)(cheng)消化循環腔(qiang)(qiang)(qiang)，腔(qiang)(qiang)(qiang)腸(chang)(chang)一端(duan)為(wei)(wei)(wei)(wei)口(kou)，他端(duan)閉塞，無(wu)肛門(men)。體(ti)(ti)壁中(zhong)(zhong)有(you)(you)(you)刺(ci)細胞(bao)。腔(qiang)(qiang)(qiang)腸(chang)(chang)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)骨骼主要為(wei)(wei)(wei)(wei)外(wai)骨骼，具有(you)(you)(you)支持(chi)和(he)(he)保護(hu)功能。多(duo)由(you)幾丁質、角質和(he)(he)石(shi)灰質構(gou)成。在(zai)很(hen)多(duo)珊(shan)瑚(hu)蟲中(zhong)(zhong)具有(you)(you)(you)骨針或(huo)骨軸(zhou)，它們存在(zai)于(yu)(yu)中(zhong)(zhong)膠層(ceng)(ceng)(ceng)(ceng)，或(huo)突出(chu)于(yu)(yu)體(ti)(ti)表面。有(you)(you)(you)無(wu)性和(he)(he)有(you)(you)(you)性兩種(zhong)(zhong)生(sheng)(sheng)殖(zhi)方(fang)式，并往往出(chu)現(xian)在(zai)同一種(zhong)(zhong)的(de)(de)(de)(de)生(sheng)(sheng)活(huo)史(shi)中(zhong)(zhong)，即水(shui)(shui)(shui)(shui)螅(xi)型(xing)(xing)世代用無(wu)性出(chu)芽生(sheng)(sheng)殖(zhi)方(fang)式產(chan)生(sheng)(sheng)水(shui)(shui)(shui)(shui)母(mu)型(xing)(xing)世代，而水(shui)(shui)(shui)(shui)母(mu)型(xing)(xing)個(ge)體(ti)(ti)脫(tuo)離(li)母(mu)體(ti)(ti)，長(chang)大成熟以(yi)后(hou)，又以(yi)有(you)(you)(you)性生(sheng)(sheng)殖(zhi)方(fang)式產(chan)生(sheng)(sheng)水(shui)(shui)(shui)(shui)螅(xi)型(xing)(xing)個(ge)體(ti)(ti)，兩個(ge)世代互相交替完成整個(ge)生(sheng)(sheng)活(huo)史(shi)。約1萬種(zhong)(zhong)，可(ke)(ke)分為(wei)(wei)(wei)(wei)：水(shui)(shui)(shui)(shui)螅(xi)蟲綱(gang)(gang)、缽水(shui)(shui)(shui)(shui)母(mu)綱(gang)(gang)和(he)(he)珊(shan)瑚(hu)蟲綱(gang)(gang)3綱(gang)(gang)，一般(ban)認為(wei)(wei)(wei)(wei)水(shui)(shui)(shui)(shui)螅(xi)蟲綱(gang)(gang)是(shi)最(zui)原(yuan)始的(de)(de)(de)(de)。絕大部(bu)分海(hai)(hai)產(chan)，只有(you)(you)(you)少(shao)數(shu)種(zhong)(zhong)類(lei)產(chan)于(yu)(yu)淡水(shui)(shui)(shui)(shui)，以(yi)熱帶(dai)和(he)(he)亞熱帶(dai)海(hai)(hai)洋(yang)的(de)(de)(de)(de)淺水(shui)(shui)(shui)(shui)區最(zui)豐富。較小種(zhong)(zhong)類(lei)可(ke)(ke)作(zuo)(zuo)(zuo)(zuo)魚類(lei)食(shi)餌，珊(shan)瑚(hu)骨骼（如紅珊(shan)瑚(hu)）可(ke)(ke)作(zuo)(zuo)(zuo)(zuo)工藝(yi)品(pin)，古珊(shan)瑚(hu)和(he)(he)現(xian)代珊(shan)瑚(hu)可(ke)(ke)形成儲油層(ceng)(ceng)(ceng)(ceng)，海(hai)(hai)邊的(de)(de)(de)(de)珊(shan)瑚(hu)礁可(ke)(ke)作(zuo)(zuo)(zuo)(zuo)天然海(hai)(hai)堤；海(hai)(hai)蜇鹽漬后(hou)成為(wei)(wei)(wei)(wei)食(shi)品(pin)，有(you)(you)(you)些種(zhong)(zhong)類(lei)可(ke)(ke)作(zuo)(zuo)(zuo)(zuo)藥用；有(you)(you)(you)些浮(fu)游水(shui)(shui)(shui)(shui)母(mu)類(lei)可(ke)(ke)作(zuo)(zuo)(zuo)(zuo)為(wei)(wei)(wei)(wei)海(hai)(hai)流指示(shi)生(sheng)(sheng)物(wu)(wu)(wu)(wu)；但是(shi)，有(you)(you)(you)些大型(xing)(xing)水(shui)(shui)(shui)(shui)母(mu)（如霞水(shui)(shui)(shui)(shui)母(mu)、根(gen)口(kou)水(shui)(shui)(shui)(shui)母(mu)）在(zai)大量出(chu)現(xian)時，會阻塞或(huo)破壞漁(yu)網，有(you)(you)(you)的(de)(de)(de)(de)海(hai)(hai)葵混于(yu)(yu)漁(yu)獲物(wu)(wu)(wu)(wu)中(zhong)(zhong)，人食(shi)后(hou)中(zhong)(zhong)毒致死。刺(ci)胞(bao)動(dong)(dong)(dong)(dong)物(wu)(wu)(wu)(wu)除極少(shao)數(shu)種(zhong)(zhong)類(lei)為(wei)(wei)(wei)(wei)淡水(shui)(shui)(shui)(shui)生(sheng)(sheng)活(huo)外(wai)，絕大多(duo)數(shu)種(zhong)(zhong)均為(wei)(wei)(wei)(wei)海(hai)(hai)洋(yang)生(sheng)(sheng)活(huo)，多(duo)數(shu)在(zai)淺海(hai)(hai)，少(shao)數(shu)為(wei)(wei)(wei)(wei)深海(hai)(hai)種(zhong)(zhong)，現(xian)存約11000種(zhong)(zhong)，分為(wei)(wei)(wei)(wei)3個(ge)綱(gang)(gang)：水(shui)(shui)(shui)(shui)螅(xi)綱(gang)(gang)（Hydrozoa）、缽水(shui)(shui)(shui)(shui)母(mu)綱(gang)(gang)（Scyphozoa）、珊(shan)瑚(hu)綱(gang)(gang)（Anthozoa）。

形態及特征

肌肉與運動

刺胞動(dong)(dong)(dong)物很少能(neng)做(zuo)主動(dong)(dong)(dong)的(de)(de)(de)(de)移(yi)位運動(dong)(dong)(dong)，運動(dong)(dong)(dong)的(de)(de)(de)(de)能(neng)力(li)(li)是(shi)很有(you)(you)限的(de)(de)(de)(de)，特別是(shi)水(shui)(shui)螅(xi)型。運動(dong)(dong)(dong)是(shi)由表皮(pi)肌(ji)肉(rou)細胞中(zhong)肌(ji)原(yuan)纖(xian)維(wei)的(de)(de)(de)(de)收(shou)縮(suo)所(suo)(suo)引(yin)起(qi)(qi)。例如(ru)(ru)(ru)水(shui)(shui)螅(xi)的(de)(de)(de)(de)身(shen)體(ti)可(ke)做(zuo)伸縮(suo)運動(dong)(dong)(dong)，伸展(zhan)時體(ti)長可(ke)達15～20mm，收(shou)縮(suo)時體(ti)長僅(jin)0.5mm，這種伸縮(suo)是(shi)爆(bao)發(fa)式的(de)(de)(de)(de)，每5～10分鐘左右爆(bao)發(fa)一(yi)次(ci)，主要是(shi)由外皮(pi)肌(ji)細胞的(de)(de)(de)(de)縱行肌(ji)原(yuan)纖(xian)維(wei)的(de)(de)(de)(de)收(shou)縮(suo)所(suo)(suo)引(yin)起(qi)(qi)。身(shen)體(ti)一(yi)側的(de)(de)(de)(de)肌(ji)原(yuan)纖(xian)維(wei)的(de)(de)(de)(de)收(shou)縮(suo)可(ke)引(yin)起(qi)(qi)身(shen)體(ti)的(de)(de)(de)(de)彎曲。有(you)(you)時靠(kao)彎曲身(shen)體(ti)及觸手(shou)并與基盤(pan)的(de)(de)(de)(de)交替附著(zhu)而(er)做(zuo)翻斛斗式的(de)(de)(de)(de)運動(dong)(dong)(dong)。基盤(pan)處粘細胞可(ke)分泌大量的(de)(de)(de)(de)氣(qi)泡，可(ke)使(shi)水(shui)(shui)螅(xi)在(zai)水(shui)(shui)面上做(zuo)短暫的(de)(de)(de)(de)漂浮。缽(bo)水(shui)(shui)母(mu)類和珊(shan)瑚類的(de)(de)(de)(de)肌(ji)原(yuan)纖(xian)維(wei)已與表皮(pi)細胞分離形(xing)(xing)成獨立的(de)(de)(de)(de)一(yi)層(ceng)肌(ji)纖(xian)維(wei)，例如(ru)(ru)(ru)水(shui)(shui)母(mu)的(de)(de)(de)(de)肌(ji)原(yuan)纖(xian)維(wei)在(zai)下(xia)傘(san)面及傘(san)緣(yuan)形(xing)(xing)成薄薄的(de)(de)(de)(de)一(yi)層(ceng)肌(ji)肉(rou)環，有(you)(you)的(de)(de)(de)(de)被(bei)輻管分離成片狀，其(qi)纖(xian)維(wei)有(you)(you)橫紋，它(ta)(ta)們做(zuo)有(you)(you)規律的(de)(de)(de)(de)收(shou)縮(suo)，使(shi)傘(san)面有(you)(you)節奏的(de)(de)(de)(de)收(shou)縮(suo)運動(dong)(dong)(dong)。當(dang)(dang)傘(san)緣(yuan)收(shou)縮(suo)時，傘(san)緣(yuan)內的(de)(de)(de)(de)水(shui)(shui)被(bei)噴(pen)出，由于反(fan)作用力(li)(li)而(er)推動(dong)(dong)(dong)水(shui)(shui)母(mu)體(ti)向上運動(dong)(dong)(dong)，當(dang)(dang)傘(san)及傘(san)緣(yuan)肌(ji)肉(rou)舒(shu)張(zhang)，被(bei)壓(ya)縮(suo)的(de)(de)(de)(de)中(zhong)膠層(ceng)的(de)(de)(de)(de)彈性，使(shi)傘(san)又(you)恢復了原(yuan)形(xing)(xing)，水(shui)(shui)又(you)重(zhong)新進(jin)入傘(san)緣(yuan)內，身(shen)體(ti)下(xia)沉，但由于收(shou)縮(suo)比(bi)舒(shu)張(zhang)要快，所(suo)(suo)以水(shui)(shui)母(mu)還是(shi)可(ke)以向上垂(chui)直運動(dong)(dong)(dong)。水(shui)(shui)母(mu)類的(de)(de)(de)(de)垂(chui)直運動(dong)(dong)(dong)在(zai)有(you)(you)緣(yuan)膜的(de)(de)(de)(de)水(shui)(shui)母(mu)可(ke)以看的(de)(de)(de)(de)更為(wei)清楚。一(yi)旦肌(ji)肉(rou)停止收(shou)縮(suo)，水(shui)(shui)母(mu)就會(hui)自然下(xia)沉。其(qi)水(shui)(shui)平方向的(de)(de)(de)(de)運動(dong)(dong)(dong)多(duo)是(shi)被(bei)動(dong)(dong)(dong)的(de)(de)(de)(de)，多(duo)是(shi)由于水(shui)(shui)流及風力(li)(li)所(suo)(suo)推動(dong)(dong)(dong)。又(you)例如(ru)(ru)(ru)在(zai)珊(shan)瑚類，海(hai)葵(kui)(kui)的(de)(de)(de)(de)肌(ji)原(yuan)纖(xian)維(wei)在(zai)隔膜上形(xing)(xing)成發(fa)達的(de)(de)(de)(de)牽縮(suo)肌(ji)，它(ta)(ta)的(de)(de)(de)(de)收(shou)縮(suo)非常有(you)(you)力(li)(li)，所(suo)(suo)以當(dang)(dang)海(hai)葵(kui)(kui)固(gu)著(zhu)在(zai)巖石上是(shi)很難將它(ta)(ta)取下(xia)的(de)(de)(de)(de)。

取食與消化

刺(ci)胞(bao)動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)都是肉食(shi)(shi)(shi)性(xing)的(de)(de)(de)(de)(de)(de)(de)，以浮游生物(wu)(wu)(wu)(wu)(wu)(wu)(wu)，小(xiao)(xiao)的(de)(de)(de)(de)(de)(de)(de)甲殼類(lei)、多(duo)(duo)(duo)毛類(lei)甚(shen)至小(xiao)(xiao)的(de)(de)(de)(de)(de)(de)(de)魚類(lei)為食(shi)(shi)(shi)。由(you)于食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)機(ji)械刺(ci)激和化(hua)學刺(ci)激，引起水(shui)螅(xi)類(lei)動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)伸長觸手(shou)，并放(fang)出刺(ci)絲(si)(si)囊以纏(chan)繞、麻痹、毒殺捕獲物(wu)(wu)(wu)(wu)(wu)(wu)(wu)，再將食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)送入(ru)(ru)口中(zhong)。口區腺細(xi)胞(bao)分泌(mi)的(de)(de)(de)(de)(de)(de)(de)粘液有(you)利(li)于食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)吞(tun)咽，食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)進入(ru)(ru)胃(wei)(wei)腔(qiang)后(hou)，胃(wei)(wei)層(ceng)的(de)(de)(de)(de)(de)(de)(de)腺細(xi)胞(bao)開(kai)(kai)始分泌(mi)蛋白酶(mei)，分解、消(xiao)化(hua)食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)使之形成許(xu)多(duo)(duo)(duo)多(duo)(duo)(duo)肽，同時在(zai)(zai)胃(wei)(wei)腔(qiang)中(zhong)由(you)于營(ying)養肌肉細(xi)胞(bao)的(de)(de)(de)(de)(de)(de)(de)鞭毛運動(dong)(dong)，食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)得(de)以混合與推動(dong)(dong)。經這種細(xi)胞(bao)外消(xiao)化(hua)之后(hou)，開(kai)(kai)始細(xi)胞(bao)內(nei)的(de)(de)(de)(de)(de)(de)(de)消(xiao)化(hua)過(guo)程(cheng)，營(ying)養肌肉細(xi)胞(bao)的(de)(de)(de)(de)(de)(de)(de)偽足吞(tun)噬(shi)食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)顆(ke)粒，在(zai)(zai)細(xi)胞(bao)內(nei)形成大量的(de)(de)(de)(de)(de)(de)(de)食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)泡(pao)，經過(guo)酸性(xing)及(ji)堿性(xing)的(de)(de)(de)(de)(de)(de)(de)化(hua)學過(guo)程(cheng)之后(hou)，營(ying)養物(wu)(wu)(wu)(wu)(wu)(wu)(wu)質由(you)細(xi)胞(bao)的(de)(de)(de)(de)(de)(de)(de)擴散(san)作(zuo)用(yong)(yong)輸送到全(quan)身。缽水(shui)母類(lei)及(ji)珊(shan)(shan)瑚類(lei)胃(wei)(wei)腔(qiang)結構比較復雜。缽水(shui)母的(de)(de)(de)(de)(de)(de)(de)胃(wei)(wei)腔(qiang)中(zhong)有(you)各(ge)種輻管及(ji)環管，胃(wei)(wei)囊中(zhong)有(you)內(nei)胚(pei)層(ceng)起源的(de)(de)(de)(de)(de)(de)(de)胃(wei)(wei)絲(si)(si)；珊(shan)(shan)瑚類(lei)的(de)(de)(de)(de)(de)(de)(de)胃(wei)(wei)腔(qiang)被許(xu)多(duo)(duo)(duo)隔(ge)膜分隔(ge)成許(xu)多(duo)(duo)(duo)小(xiao)(xiao)室，隔(ge)膜上有(you)隔(ge)膜絲(si)(si)。胃(wei)(wei)絲(si)(si)及(ji)隔(ge)膜絲(si)(si)中(zhong)含有(you)大量的(de)(de)(de)(de)(de)(de)(de)刺(ci)細(xi)胞(bao)及(ji)腺細(xi)胞(bao)，它們是將食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)吞(tun)入(ru)(ru)胃(wei)(wei)腔(qiang)之后(hou)才(cai)殺死及(ji)消(xiao)化(hua)。消(xiao)化(hua)后(hou)的(de)(de)(de)(de)(de)(de)(de)營(ying)養物(wu)(wu)(wu)(wu)(wu)(wu)(wu)通過(guo)各(ge)種管道輸送到全(quan)身，未消(xiao)化(hua)的(de)(de)(de)(de)(de)(de)(de)食(shi)(shi)(shi)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)殘渣仍由(you)口排出。糖元及(ji)脂肪是腔(qiang)腸動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)(de)主要(yao)貯存物(wu)(wu)(wu)(wu)(wu)(wu)(wu)。刺(ci)胞(bao)動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)中(zhong)許(xu)多(duo)(duo)(duo)種類(lei)，特別是海洋中(zhong)的(de)(de)(de)(de)(de)(de)(de)造礁珊(shan)(shan)瑚類(lei)，體(ti)內(nei)均有(you)共生的(de)(de)(de)(de)(de)(de)(de)藻類(lei)，如動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)黃藻、腰鞭毛藻之類(lei)。藻類(lei)能進行光(guang)合作(zuo)用(yong)(yong)，產生甘油、脂肪、糖及(ji)脯氨酸等(deng)，并提(ti)供給(gei)刺(ci)胞(bao)動(dong)(dong)物(wu)(wu)(wu)(wu)(wu)(wu)(wu)作(zuo)為其補充營(ying)養。這將在(zai)(zai)珊(shan)(shan)瑚綱中(zhong)做(zuo)進一步(bu)的(de)(de)(de)(de)(de)(de)(de)敘述。

呼吸與排泄

刺(ci)胞(bao)動物沒有專門的(de)呼(hu)吸及排泄器官，由于(yu)身體(ti)是(shi)由兩層細(xi)胞(bao)圍(wei)繞胃(wei)循環腔(qiang)所組成，并通過(guo)口(kou)使(shi)胃(wei)腔(qiang)與外界相通，實際上體(ti)壁的(de)兩層細(xi)胞(bao)均與外界環境接觸，所以(yi)呼(hu)吸與排泄作(zuo)用可(ke)以(yi)由體(ti)壁細(xi)胞(bao)直接獨立進行。出、入(ru)口(kou)及胃(wei)腔(qiang)的(de)水流可(ke)以(yi)攜帶入(ru)新鮮的(de)氧氣，并帶走代謝產(chan)物。刺(ci)胞(bao)動物的(de)主要含氮廢物是(shi)氨。

神經傳導及感官

刺(ci)(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)是(shi)(shi)(shi)最早出(chu)現(xian)神(shen)(shen)(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)構的(de)(de)(de)(de)(de)(de)多(duo)(duo)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)。神(shen)(shen)(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)構原始，是(shi)(shi)(shi)由(you)(you)雙(shuang)極神(shen)(shen)(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)(yuan)、多(duo)(duo)極神(shen)(shen)(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)(yuan)及(ji)(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)纖(xian)維(wei)聯合(he)成(cheng)(cheng)神(shen)(shen)(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)神(shen)(shen)(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)(wang)，一(yi)(yi)(yi)(yi)(yi)般位(wei)(wei)(wei)于外(wai)表皮(pi)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)基部肌(ji)肉(rou)層之外(wai)，呈網(wang)(wang)(wang)狀(zhuang)分布，故(gu)稱(cheng)網(wang)(wang)(wang)狀(zhuang)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)系統(tong)（netnervous system）。由(you)(you)于神(shen)(shen)(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)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)向(xiang)(xiang)各個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)方(fang)向(xiang)(xiang)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)，也(ye)(ye)稱(cheng)為(wei)漫(man)散神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)系統(tong)（diffusenervous system）。水(shui)(shui)(shui)(shui)(shui)螅就只(zhi)(zhi)有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(wang)，但(dan)大多(duo)(duo)數腔腸動(dong)(dong)物(wu)除了表皮(pi)的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)(wang)之外(wai)，在(zai)(zai)(zai)(zai)胃層的(de)(de)(de)(de)(de)(de)基部也(ye)(ye)有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(wang)，這(zhe)兩(liang)(liang)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(wang)或(huo)(huo)(huo)是(shi)(shi)(shi)完(wan)全獨(du)立的(de)(de)(de)(de)(de)(de)，或(huo)(huo)(huo)有(you)(you)(you)(you)(you)(you)纖(xian)維(wei)相聯。1971年(nian)Westfall等首先(xian)證明了水(shui)(shui)(shui)(shui)(shui)螅及(ji)(ji)其(qi)(qi)他(ta)腔腸動(dong)(dong)物(wu)在(zai)(zai)(zai)(zai)神(shen)(shen)(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)(yuan)之間(jian)(jian)、神(shen)(shen)(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)(yuan)與效應(ying)器(qi)（表皮(pi)肌(ji)肉(rou)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)、刺(ci)(ci)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)、腺細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)等）之間(jian)(jian)也(ye)(ye)存在(zai)(zai)(zai)(zai)著(zhu)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)傳(chuan)(chuan)遞(di)（synaptic transmission）。即(ji)(ji)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)沖動(dong)(dong)的(de)(de)(de)(de)(de)(de)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)是(shi)(shi)(shi)由(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(yuan)的(de)(de)(de)(de)(de)(de)軸突(tu)(tu)(tu)(tu)(tu)，傳(chuan)(chuan)遞(di)給另一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(yuan)的(de)(de)(de)(de)(de)(de)樹突(tu)(tu)(tu)(tu)(tu)。軸突(tu)(tu)(tu)(tu)(tu)的(de)(de)(de)(de)(de)(de)末(mo)端(duan)具(ju)(ju)(ju)有(you)(you)(you)(you)(you)(you)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)小泡(pao)（synaptic vesicle），樹突(tu)(tu)(tu)(tu)(tu)的(de)(de)(de)(de)(de)(de)末(mo)端(duan)沒(mei)有(you)(you)(you)(you)(you)(you)。傳(chuan)(chuan)導(dao)(dao)(dao)(dao)時，突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)小泡(pao)釋放乙酰膽堿引(yin)起(qi)(qi)(qi)后(hou)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(yuan)的(de)(de)(de)(de)(de)(de)興(xing)奮，沖動(dong)(dong)傳(chuan)(chuan)出(chu)以后(hou)，乙酰膽堿被(bei)神(shen)(shen)(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)稍表面(mian)(mian)(mian)的(de)(de)(de)(de)(de)(de)膽堿酯(zhi)酶水(shui)(shui)(shui)(shui)(shui)解成(cheng)(cheng)膽堿及(ji)(ji)乙酸而(er)解除了激(ji)活作(zuo)用(yong)。以后(hou)又發(fa)現(xian)腔腸動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)分為(wei)兩(liang)(liang)種(zhong)(zhong)類(lei)型(xing)。一(yi)(yi)(yi)(yi)(yi)類(lei)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)是(shi)(shi)(shi)對(dui)稱(cheng)性(xing)(xing)(xing)的(de)(de)(de)(de)(de)(de)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)（symmetrical），即(ji)(ji)兩(liang)(liang)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)端(duan)有(you)(you)(you)(you)(you)(you)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)小泡(pao)，因此沖動(dong)(dong)可(ke)以同時向(xiang)(xiang)兩(liang)(liang)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)幾(ji)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)方(fang)向(xiang)(xiang)傳(chuan)(chuan)遞(di)，這(zhe)種(zhong)(zhong)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)也(ye)(ye)叫(jiao)非(fei)極性(xing)(xing)(xing)的(de)(de)(de)(de)(de)(de)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)（nonpolarized transmission）；另一(yi)(yi)(yi)(yi)(yi)類(lei)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)是(shi)(shi)(shi)不對(dui)稱(cheng)的(de)(de)(de)(de)(de)(de)（asymmetrical），即(ji)(ji)神(shen)(shen)(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)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)只(zhi)(zhi)有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)末(mo)端(duan)具(ju)(ju)(ju)突(tu)(tu)(tu)(tu)(tu)觸(chu)(chu)(chu)(chu)小泡(pao)，神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)沖動(dong)(dong)只(zhi)(zhi)能向(xiang)(xiang)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)方(fang)向(xiang)(xiang)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)，因此也(ye)(ye)稱(cheng)為(wei)有(you)(you)(you)(you)(you)(you)極性(xing)(xing)(xing)的(de)(de)(de)(de)(de)(de)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)（polarized transmission）。最近的(de)(de)(de)(de)(de)(de)研(yan)究證明刺(ci)(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)非(fei)極性(xing)(xing)(xing)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)是(shi)(shi)(shi)很普遍的(de)(de)(de)(de)(de)(de)。也(ye)(ye)有(you)(you)(you)(you)(you)(you)人認(ren)為(wei)刺(ci)(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)兩(liang)(liang)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(wang)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)是(shi)(shi)(shi)由(you)(you)多(duo)(duo)極神(shen)(shen)(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)(yuan)形成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)非(fei)極性(xing)(xing)(xing)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)，也(ye)(ye)就是(shi)(shi)(shi)慢(man)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)系統(tong)；另一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)是(shi)(shi)(shi)由(you)(you)雙(shuang)極神(shen)(shen)(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)(yuan)形成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)極性(xing)(xing)(xing)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)，也(ye)(ye)就是(shi)(shi)(shi)快傳(chuan)(chuan)導(dao)(dao)(dao)(dao)系統(tong)。刺(ci)(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)(yuan)可(ke)以有(you)(you)(you)(you)(you)(you)2個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)、3個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)或(huo)(huo)(huo)多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)長(chang)的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)(qi)，這(zhe)些(xie)突(tu)(tu)(tu)(tu)(tu)起(qi)(qi)(qi)或(huo)(huo)(huo)與感(gan)(gan)官(guan)(guan)相聯、或(huo)(huo)(huo)與效應(ying)器(qi)相聯、或(huo)(huo)(huo)與其(qi)(qi)他(ta)神(shen)(shen)(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)(yuan)相聯、或(huo)(huo)(huo)者(zhe)是(shi)(shi)(shi)同一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)(yuan)同時與感(gan)(gan)官(guan)(guan)與效應(ying)器(qi)相聯，這(zhe)種(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)說明了神(shen)(shen)(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)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)的(de)(de)(de)(de)(de)(de)原始性(xing)(xing)(xing)。在(zai)(zai)(zai)(zai)生(sheng)理意義上(shang)(shang)代表了高等動(dong)(dong)物(wu)所具(ju)(ju)(ju)有(you)(you)(you)(you)(you)(you)的(de)(de)(de)(de)(de)(de)感(gan)(gan)覺(jue)神(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)(shen)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)、運動(dong)(dong)神(shen)(shen)(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)(ji)中(zhong)樞神(shen)(shen)(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)(de)(de)起(qi)(qi)(qi)始階段。此外(wai)，刺(ci)(ci)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)非(fei)神(shen)(shen)(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)導(dao)(dao)(dao)(dao)，即(ji)(ji)上(shang)(shang)皮(pi)傳(chuan)(chuan)導(dao)(dao)(dao)(dao)也(ye)(ye)是(shi)(shi)(shi)很常見(jian)的(de)(de)(de)(de)(de)(de)，例(li)如刺(ci)(ci)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)、表皮(pi)肌(ji)肉(rou)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)以完(wan)全獨(du)立于神(shen)(shen)(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)(yuan)而(er)被(bei)自(zi)身(shen)所控制(zhi)。水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)構比水(shui)(shui)(shui)(shui)(shui)螅型(xing)復(fu)雜，例(li)如水(shui)(shui)(shui)(shui)(shui)螅水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)，除了傘(san)(san)部的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)(wang)之外(wai)，傘(san)(san)緣的(de)(de)(de)(de)(de)(de)上(shang)(shang)皮(pi)神(shen)(shen)(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)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)分別在(zai)(zai)(zai)(zai)傘(san)(san)緣的(de)(de)(de)(de)(de)(de)上(shang)(shang)、下(xia)(xia)(xia)面(mian)(mian)(mian)集中(zhong)形成(cheng)(cheng)兩(liang)(liang)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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(xia)(xia)(xia)面(mian)(mian)(mian)（或(huo)(huo)(huo)稱(cheng)外(wai)面(mian)(mian)(mian)）的(de)(de)(de)(de)(de)(de)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)母(mu)(mu)(mu)類(lei)的(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)多(duo)(duo)數沒(mei)有(you)(you)(you)(you)(you)(you)這(zhe)種(zhong)(zhong)神(shen)(shen)(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)在(zai)(zai)(zai)(zai)傘(san)(san)緣集中(zhong)形成(cheng)(cheng)4～8個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)。水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)體(ti)均能表現(xian)出(chu)一(yi)(yi)(yi)(yi)(yi)種(zhong)(zhong)有(you)(you)(you)(you)(you)(you)節(jie)(jie)奏的(de)(de)(de)(de)(de)(de)收(shou)(shou)縮運動(dong)(dong)，這(zhe)是(shi)(shi)(shi)由(you)(you)于水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)構每(mei)隔一(yi)(yi)(yi)(yi)(yi)定時間(jian)(jian)能自(zi)發(fa)地產生(sheng)動(dong)(dong)作(zuo)電位(wei)(wei)(wei)，并(bing)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)過(guo)(guo)神(shen)(shen)(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)導(dao)(dao)(dao)(dao)引(yin)起(qi)(qi)(qi)整個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)身(shen)體(ti)的(de)(de)(de)(de)(de)(de)收(shou)(shou)縮。研(yan)究已(yi)經(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)(jing)證明這(zhe)種(zhong)(zhong)自(zi)發(fa)的(de)(de)(de)(de)(de)(de)動(dong)(dong)作(zuo)電位(wei)(wei)(wei)是(shi)(shi)(shi)由(you)(you)起(qi)(qi)(qi)博(bo)點的(de)(de)(de)(de)(de)(de)神(shen)(shen)(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)(yuan)所引(yin)起(qi)(qi)(qi)。起(qi)(qi)(qi)博(bo)點神(shen)(shen)(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)(yuan)在(zai)(zai)(zai)(zai)水(shui)(shui)(shui)(shui)(shui)螅水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)存在(zai)(zai)(zai)(zai)于外(wai)神(shen)(shen)(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)，在(zai)(zai)(zai)(zai)缽水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)存在(zai)(zai)(zai)(zai)于感(gan)(gan)官(guan)(guan)神(shen)(shen)(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)中(zhong)。而(er)且每(mei)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)神(shen)(shen)(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)（一(yi)(yi)(yi)(yi)(yi)般4～8個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)）都(dou)有(you)(you)(you)(you)(you)(you)起(qi)(qi)(qi)博(bo)神(shen)(shen)(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)(yuan)，它是(shi)(shi)(shi)水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)有(you)(you)(you)(you)(you)(you)節(jie)(jie)奏博(bo)動(dong)(dong)的(de)(de)(de)(de)(de)(de)中(zhong)心(xin)。一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)體(ti)似(si)乎有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)起(qi)(qi)(qi)博(bo)點就足以引(yin)起(qi)(qi)(qi)身(shen)體(ti)有(you)(you)(you)(you)(you)(you)節(jie)(jie)奏的(de)(de)(de)(de)(de)(de)收(shou)(shou)縮運動(dong)(dong)，但(dan)實(shi)驗證明多(duo)(duo)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)起(qi)(qi)(qi)博(bo)點比僅有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)起(qi)(qi)(qi)博(bo)點能使(shi)(shi)收(shou)(shou)縮的(de)(de)(de)(de)(de)(de)節(jie)(jie)奏更(geng)有(you)(you)(you)(you)(you)(you)規(gui)律、更(geng)有(you)(you)(you)(you)(you)(you)保障、使(shi)(shi)間(jian)(jian)隔的(de)(de)(de)(de)(de)(de)時間(jian)(jian)也(ye)(ye)較短。腔腸動(dong)(dong)物(wu)的(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)(shui)(shui)螅型(xing)體(ti)沒(mei)有(you)(you)(you)(you)(you)(you)明顯的(de)(de)(de)(de)(de)(de)感(gan)(gan)官(guan)(guan)，其(qi)(qi)感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)可(ke)分布全身(shen)，但(dan)觸(chu)(chu)(chu)(chu)手、口(kou)區(qu)較為(wei)豐富(fu)。水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)型(xing)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)體(ti)，在(zai)(zai)(zai)(zai)傘(san)(san)緣具(ju)(ju)(ju)有(you)(you)(you)(you)(you)(you)豐富(fu)的(de)(de)(de)(de)(de)(de)感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)或(huo)(huo)(huo)感(gan)(gan)覺(jue)器(qi)官(guan)(guan)。感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)(de)(de)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)體(ti)都(dou)是(shi)(shi)(shi)具(ju)(ju)(ju)纖(xian)毛的(de)(de)(de)(de)(de)(de)。感(gan)(gan)覺(jue)器(qi)官(guan)(guan)包(bao)括眼點及(ji)(ji)平衡(heng)(heng)囊(nang)(nang)。眼點是(shi)(shi)(shi)由(you)(you)感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)構成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)杯狀(zhuang)物(wu)，內有(you)(you)(you)(you)(you)(you)色(se)素顆粒分布，它對(dui)光(guang)(guang)線或(huo)(huo)(huo)有(you)(you)(you)(you)(you)(you)正趨性(xing)(xing)(xing)，即(ji)(ji)有(you)(you)(you)(you)(you)(you)光(guang)(guang)時游(you)向(xiang)(xiang)水(shui)(shui)(shui)(shui)(shui)面(mian)(mian)(mian)。或(huo)(huo)(huo)對(dui)光(guang)(guang)有(you)(you)(you)(you)(you)(you)負趨性(xing)(xing)(xing)，即(ji)(ji)有(you)(you)(you)(you)(you)(you)光(guang)(guang)時下(xia)(xia)(xia)沉(chen)水(shui)(shui)(shui)(shui)(shui)底(di)，無(wu)光(guang)(guang)或(huo)(huo)(huo)弱光(guang)(guang)時浮向(xiang)(xiang)水(shui)(shui)(shui)(shui)(shui)面(mian)(mian)(mian)。平衡(heng)(heng)囊(nang)(nang)在(zai)(zai)(zai)(zai)水(shui)(shui)(shui)(shui)(shui)螅水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)結(jie)(jie)構簡單，在(zai)(zai)(zai)(zai)緣膜基部或(huo)(huo)(huo)下(xia)(xia)(xia)傘(san)(san)面(mian)(mian)(mian)神(shen)(shen)(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)神(shen)(shen)(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)個(ge)(ge)(ge)(ge)(ge)(ge)(ge)(ge)小囊(nang)(nang)，囊(nang)(nang)的(de)(de)(de)(de)(de)(de)內壁有(you)(you)(you)(you)(you)(you)感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)，細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)上(shang)(shang)也(ye)(ye)有(you)(you)(you)(you)(you)(you)纖(xian)毛。囊(nang)(nang)的(de)(de)(de)(de)(de)(de)底(di)部有(you)(you)(you)(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)鈣質結(jie)(jie)石(shi)。它是(shi)(shi)(shi)一(yi)(yi)(yi)(yi)(yi)種(zhong)(zhong)重(zhong)力(li)感(gan)(gan)受(shou)器(qi)。當傘(san)(san)緣傾(qing)斜時，結(jie)(jie)石(shi)與感(gan)(gan)覺(jue)細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)的(de)(de)(de)(de)(de)(de)纖(xian)毛接觸(chu)(chu)(chu)(chu)，并(bing)刺(ci)(ci)激(ji)纖(xian)毛細(xi)胞(bao)(bao)(bao)(bao)(bao)(bao)(bao)(bao)以產生(sheng)動(dong)(dong)作(zuo)電位(wei)(wei)(wei)，抑(yi)制(zhi)了該側肌(ji)肉(rou)纖(xian)維(wei)的(de)(de)(de)(de)(de)(de)收(shou)(shou)縮，通(tong)過(guo)(guo)肌(ji)肉(rou)收(shou)(shou)縮再(zai)調(diao)整身(shen)體(ti)使(shi)(shi)恢復(fu)平衡(heng)(heng)位(wei)(wei)(wei)置。缽水(shui)(shui)(shui)(shui)(shui)母(mu)(mu)(mu)類(lei)的(de)(de)(de)(de)(de)(de)平衡(heng)(heng)囊(nang)(nang)結(jie)(jie)構更(geng)復(fu)雜，將在(zai)(zai)(zai)(zai)有(you)(you)(you)(you)(you)(you)關節(jie)(jie)中(zhong)敘(xu)述

生殖與生活史

無(wu)(wu)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)及(ji)(ji)有(you)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)在(zai)(zai)(zai)(zai)腔腸動物(wu)(wu)中都是很普(pu)遍的(de)(de)(de)(de)(de)(de)。無(wu)(wu)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)(de)(de)(de)(de)主要形(xing)式(shi)是出(chu)(chu)(chu)芽(ya)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)，特別是在(zai)(zai)(zai)(zai)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)更為(wei)常見。例(li)如(ru)(ru)(ru)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)出(chu)(chu)(chu)芽(ya)時從身體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)靠(kao)基部(bu)(bu)通(tong)過體(ti)(ti)(ti)壁(bi)及(ji)(ji)胃(wei)腔的(de)(de)(de)(de)(de)(de)向(xiang)外突出(chu)(chu)(chu)，再(zai)長(chang)出(chu)(chu)(chu)觸手與(yu)口(kou)即形(xing)成(cheng)(cheng)(cheng)芽(ya)體(ti)(ti)(ti)，以(yi)后(hou)(hou)芽(ya)體(ti)(ti)(ti)與(yu)母(mu)(mu)體(ti)(ti)(ti)分離即形(xing)成(cheng)(cheng)(cheng)新的(de)(de)(de)(de)(de)(de)個體(ti)(ti)(ti)。但(dan)在(zai)(zai)(zai)(zai)藪枝螅(xi)(xi)(xi)(xi)(xi)（Obelia）所形(xing)成(cheng)(cheng)(cheng)的(de)(de)(de)(de)(de)(de)芽(ya)體(ti)(ti)(ti)與(yu)母(mu)(mu)體(ti)(ti)(ti)不(bu)分離則形(xing)成(cheng)(cheng)(cheng)了(le)群體(ti)(ti)(ti)。其次，也可(ke)以(yi)通(tong)過分裂方式(shi)進行(xing)無(wu)(wu)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)，主要發(fa)生(sheng)(sheng)(sheng)(sheng)(sheng)在(zai)(zai)(zai)(zai)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)，例(li)如(ru)(ru)(ru)海葵(kui)可(ke)以(yi)縱(zong)分裂，缽水(shui)(shui)(shui)母(mu)(mu)的(de)(de)(de)(de)(de)(de)幼(you)(you)體(ti)(ti)(ti)以(yi)橫分裂進行(xing)無(wu)(wu)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)。此外水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)一(yi)(yi)般具有(you)很強(qiang)的(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)能力，例(li)如(ru)(ru)(ru)，將水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)切成(cheng)(cheng)(cheng)數(shu)(shu)段(duan)(duan)，條件合(he)宜時每段(duan)(duan)都可(ke)以(yi)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)成(cheng)(cheng)(cheng)一(yi)(yi)個新的(de)(de)(de)(de)(de)(de)個體(ti)(ti)(ti)，再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)時口(kou)與(yu)反(fan)口(kou)端(duan)的(de)(de)(de)(de)(de)(de)極(ji)性(xing)不(bu)變，但(dan)口(kou)端(duan)的(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)速度比反(fan)口(kou)端(duan)迅(xun)速。所以(yi)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)的(de)(de)(de)(de)(de)(de)再(zai)生(sheng)(sheng)(sheng)(sheng)(sheng)現(xian)(xian)象也被認為(wei)是無(wu)(wu)性(xing)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)(de)(de)(de)(de)一(yi)(yi)種方式(shi)。有(you)些生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)出(chu)(chu)(chu)現(xian)(xian)在(zai)(zai)(zai)(zai)多(duo)數(shu)(shu)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)及(ji)(ji)所有(you)的(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)母(mu)(mu)型(xing)，除少數(shu)(shu)種類例(li)如(ru)(ru)(ru)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)為(wei)雌(ci)雄同(tong)(tong)體(ti)(ti)(ti)之外，絕大(da)多(duo)數(shu)(shu)種類為(wei)雌(ci)雄異(yi)體(ti)(ti)(ti)（或(huo)(huo)異(yi)群體(ti)(ti)(ti)）。生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)細胞(bao)(bao)(bao)來源于(yu)(yu)間細胞(bao)(bao)(bao)，然后(hou)(hou)遷(qian)移到固定(ding)的(de)(de)(de)(de)(de)(de)位置(zhi)上(shang)形(xing)成(cheng)(cheng)(cheng)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)腺(xian)(xian)。水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)蟲(chong)(chong)綱(gang)的(de)(de)(de)(de)(de)(de)動物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)腺(xian)(xian)來源于(yu)(yu)表(biao)皮(pi)層(ceng)(ceng)，例(li)如(ru)(ru)(ru)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)，水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)水(shui)(shui)(shui)母(mu)(mu)的(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)腺(xian)(xian)位于(yu)(yu)放射管下或(huo)(huo)垂唇周圍(wei)，但(dan)都是來源于(yu)(yu)表(biao)皮(pi)層(ceng)(ceng)細胞(bao)(bao)(bao)。缽水(shui)(shui)(shui)母(mu)(mu)綱(gang)的(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)細胞(bao)(bao)(bao)起源于(yu)(yu)胃(wei)層(ceng)(ceng)位于(yu)(yu)胃(wei)囊低部(bu)(bu)。珊瑚(hu)綱(gang)的(de)(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)細胞(bao)(bao)(bao)是由(you)胃(wei)腔中的(de)(de)(de)(de)(de)(de)隔(ge)膜上(shang)發(fa)生(sheng)(sheng)(sheng)(sheng)(sheng)，也是內(nei)胚(pei)層(ceng)(ceng)來源。腔腸動物(wu)(wu)只有(you)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)腺(xian)(xian)，沒有(you)出(chu)(chu)(chu)現(xian)(xian)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)導管及(ji)(ji)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)附屬腺(xian)(xian)，生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)細胞(bao)(bao)(bao)成(cheng)(cheng)(cheng)熟之后(hou)(hou)由(you)口(kou)排出(chu)(chu)(chu)，或(huo)(huo)由(you)體(ti)(ti)(ti)壁(bi)破裂而(er)釋放。受(shou)(shou)精作用依不(bu)同(tong)(tong)的(de)(de)(de)(de)(de)(de)種而(er)異(yi)，或(huo)(huo)在(zai)(zai)(zai)(zai)體(ti)(ti)(ti)外海水(shui)(shui)(shui)中進行(xing)，或(huo)(huo)在(zai)(zai)(zai)(zai)垂管的(de)(de)(de)(de)(de)(de)表(biao)面(mian)，或(huo)(huo)在(zai)(zai)(zai)(zai)胃(wei)腔內(nei)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)腺(xian)(xian)的(de)(de)(de)(de)(de)(de)部(bu)(bu)位進行(xing)。卵裂是完(wan)全的(de)(de)(de)(de)(de)(de)，形(xing)成(cheng)(cheng)(cheng)中空的(de)(de)(de)(de)(de)(de)囊胚(pei)，經移入法(fa)或(huo)(huo)內(nei)陷法(fa)形(xing)成(cheng)(cheng)(cheng)原腸胚(pei)，結果形(xing)成(cheng)(cheng)(cheng)兩層(ceng)(ceng)細胞(bao)(bao)(bao)，即兩個胚(pei)層(ceng)(ceng)，內(nei)部(bu)(bu)成(cheng)(cheng)(cheng)團的(de)(de)(de)(de)(de)(de)細胞(bao)(bao)(bao)為(wei)內(nei)胚(pei)層(ceng)(ceng)，將來形(xing)成(cheng)(cheng)(cheng)成(cheng)(cheng)(cheng)體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)胃(wei)層(ceng)(ceng)，外表(biao)的(de)(de)(de)(de)(de)(de)一(yi)(yi)層(ceng)(ceng)為(wei)外胚(pei)層(ceng)(ceng)，將來形(xing)成(cheng)(cheng)(cheng)成(cheng)(cheng)(cheng)體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)表(biao)皮(pi)層(ceng)(ceng)。實心的(de)(de)(de)(de)(de)(de)原腸胚(pei)迅(xun)速延長(chang)，體(ti)(ti)(ti)表(biao)出(chu)(chu)(chu)現(xian)(xian)纖(xian)毛，形(xing)成(cheng)(cheng)(cheng)了(le)自(zi)由(you)游泳的(de)(de)(de)(de)(de)(de)浮浪幼(you)(you)蟲(chong)(chong)（planula）。浮浪幼(you)(you)蟲(chong)(chong)早期沒有(you)口(kou)及(ji)(ji)胃(wei)腔，游泳一(yi)(yi)段(duan)(duan)時間之后(hou)(hou)，固著在(zai)(zai)(zai)(zai)水(shui)(shui)(shui)草、巖(yan)石或(huo)(huo)其他物(wu)(wu)體(ti)(ti)(ti)上(shang)發(fa)育成(cheng)(cheng)(cheng)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)型(xing)體(ti)(ti)(ti)，或(huo)(huo)再(zai)經過出(chu)(chu)(chu)芽(ya)生(sheng)(sheng)(sheng)(sheng)(sheng)殖(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)形(xing)成(cheng)(cheng)(cheng)群體(ti)(ti)(ti)。淡水(shui)(shui)(shui)生(sheng)(sheng)(sheng)(sheng)(sheng)活的(de)(de)(de)(de)(de)(de)水(shui)(shui)(shui)螅(xi)(xi)(xi)(xi)(xi)沒有(you)幼(you)(you)蟲(chong)(chong)期，其受(shou)(shou)精卵直接(jie)發(fa)育。