GERM CELLS OF COELENTERATES 19 



of the process. Chun ('95) describes a shuilar process in Rathkea 

 octopunctata and Lizzia claparedei. He describes the origin of 

 the bud by the proliferation of a group of ectoderm cells which 

 becomes isolated as a definite mass, though still held in place 

 against the stomach wall, from which all organs of the bud are 

 developed. In these forms the enteric cavities of buds and 

 parents later unite. When sexual maturity is reached germ cells 

 are formed in the stomach wall where the bud was developed 

 earlier, but Chun does not consider the budding as due to a 

 geminal process. Rather, he believes the ectoderm and ento- 

 derm of the medusae to be alike in histological and organo- 

 genetic structure and potency. Braem ('08) reviews and con- 

 firms the work of Chun, but finds germ cells are present in the 

 stomach wall at the same time the bud is forming ; he believes the 

 group of cells which start the bud are oocytes, and looks upon 

 the budding process as a short and rapid method of producing 

 a new organism out of cells which are germinal in character. 

 Most budding, he believes, shows no relation between bud and 

 sex cells, and in these cases all layers are essential to the forma- 

 tion of the bud because each tissue has retained only the ability 

 to produce cells of its own kind. Mayer thinks Braem has 

 produced strong evidence that this sort of budding is a germinal 

 process, but does not believe the evidence is conclusive. Child 

 ('15) interprets this case as showing both sex cells and asexual 

 buds come from the functional and more or less specialized cells 

 of the parent medusa. 



Nekrassoff ('11) studied Eleutheria dichotoma, which produces 

 buds from the outer wall of the ring-canal. In this form budding 

 parallels sexual development, but does not interrupt it, nor is 

 budding interrupted by sexual development. In a single indi- 

 vidual one may find numerous buds, young and old, young and 

 old eggs, cleavage stages and young polyps — all at the same time. 

 The budding takes place in the usual way, involving both ecto- 

 derm and entoderm, and while Nekrassoff finds conditions which 

 resemble the observations of Chun and Braem in Rathkea and 

 Lizzia, he can demonstrate the continuity of bud and parent 

 tissues at all times . He does note that the ectoderm and entoderm 



