Introduction to Animal Morphology. 91 



quent non-sexual factor ever develops its antecedent. 

 In some cases, planoblasts have been observed to pro- 

 duce heteromorphic buds unlike their parents ; thus 

 Placckcl describes Cuninae as produced by budding 

 from medusae of the family Geryonidae. To this 

 process, which is not yet understood, the name 

 Alleogenesis has been given. 



Medusae can be multiplied by artificial division ; 

 even when cut into a hundred pieces, each became a 

 perfect medusa (Haeckcl). 



Gymnoblastea are divided into the following families :* 

 i. Clavidae hydrocaulus rudimental or developed; hy- 

 dranths club-like, with scattered filiform tentacles ; sporosacs 

 fixed, sessile, or shortly stalked. In Tubiclava, the hydrocaulus 

 is developed. Cordylophora, the only freshwater form, has 

 fusiform polypites at the extremities of a branched crenosarc, 

 and sporosacs on the hydrocaulus, each with a branched 

 spadix. 2. Turridoe hydrocaulus and hydranths as last ; 

 planoblasts,! with simple radiating canals, and simple 

 marginal tentacles. In Campaniclava, the hydrocaulus is 

 undeveloped, and the planoblast is bitentaculate. In Turris 

 the nectocalyx has striped muscular fibres, and each marginal 

 tentacle has a bulbous ocellated base. 3. Corynidae 

 hydranths with scattered, often spirally arranged, capitate 

 tentacles, and fixed sporosacs ; hydrocaulus developed, ex. 

 Coryne. 4. Syncorynidce hydranths with scattered, or 

 tly scattered, partly verticillate, capitate tentacles, with 

 . formerly known as Sarsia, with a simple mouth, 

 four radial canals, and marginal tentacles, ex. Syncoryne. 

 5. Dicorynichi hydrncaulus invested with a perisarc ; 

 hylranths with verticillate filiform tentacles ; planoblasts 

 natatory, ciliated, with two .simple basal tentacles, ex. Dicoryne. 



Classification is a matter of some difficulty, as similar {,'on<>-<>mrs may 

 be associated with dis-imilar trnjiho^nines ( I-M-Miiism) ; or dissimilar 

 somcs may spring from simi: .ism). 



t ( ivdrodca. 



