The porifera and coelentera . ditierent in the differentfamilies, but is generally acombination of some of the fol-lowing hydroid or medusoidindividuals. Polymorphic Modifica-tions OF THE Hydroid :— 1. The gastrozooid (siphon,polypite) has a large mouth,and is provided with nemato-cysts; at or near its base isusually placed a single tentacle(,e; 51,6-). The tentacleis generally extremely long andcontractile ; it is tubular, and iseither itself provided with bat-teriesofnematocysts(Apolemia). Fio. 44. 44.—Diagram showing possible modifica-tions of meilusoids and hydroids of a colonyof Si
The porifera and coelentera . ditierent in the differentfamilies, but is generally acombination of some of the fol-lowing hydroid or medusoidindividuals. Polymorphic Modifica-tions OF THE Hydroid :— 1. The gastrozooid (siphon,polypite) has a large mouth,and is provided with nemato-cysts; at or near its base isusually placed a single tentacle(,e; 51,6-). The tentacleis generally extremely long andcontractile ; it is tubular, and iseither itself provided with bat-teriesofnematocysts(Apolemia). Fio. 44. 44.—Diagram showing possible modifica-tions of meilusoids and hydroids of a colonyof Siphonophora. h, pneumatophore ; l, necto-phores (swininiing bells) ; I, hydrophylliuni, , 1 r r! (covering piece); i, generative medusoid ; g, or bears a large numl)er or tine dactylozoold with attached tentacle, h; , f>,.. r>i. fi>»iUln nnrrir trozooid, with branched grappling tentacle, lateral tnieadh oi lemma, cairy- y. „^_ j.^^,,, „r ^.g,.,,, i-jig thick black line ine numerous nematOCVStS represents endoderm, the thinner line , oi ^ m, 1 (After Allman.) (i orskalea). ihe latter can sometimes be spirally retracted into a protective cup or involucrum(Agalmopsis). In some cases no tentacle is developed (Velella).The endoderra of the gastrozooid is generally pigmented, and oftenprojects as villi into the coelenteron. 2. The dactylozooid (hydrocyst, palpon) is generally devoid ofa mouth, and provided liberally with nematocysts. The palp
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Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectctenophora
