PORIFERA, CCELENTERATA, VERTEBRATA 97 



views. He finds that "The egg cells of Campanularia 

 flexuosa arise in the entoderm of the pedicel of the 

 gonophore, by the transformation of a single 

 epithelial cell, or from the basal half of a divided 

 cell, the distal half of which remains an epithelial 

 cell and retains its epithelial functions. Therefore 

 the egg cells have come from differentiated body- 

 cells (so-called) and there is no differentiation of 

 the germ-plasm in the sense that germ-cells are 

 early differentiated and set aside and do not partici- 

 pate in the body functions. Any cell of the ento- 

 derm of Campanularia flexuosa may become an egg 

 cell if it is in the position of the developing gono- 

 phore " (p. 411). 



In spite of these attacks upon the germ-plasm 

 theory as applied to ccelenterates, the possibility 

 and even probability of such a condition seems to 

 the writer to exist, and he is inclined to accept 

 Downing's position in the matter. Weismann's 

 views must, however, be modified, since the germ 

 cells are not ectoderm cells, as he claims, nor do 

 they belong to any germ layer. They are, according 

 to the view adopted here, set aside as a separate 

 class of cells at some stage during early development, 

 are scattered about among the cells of the ectoderm 

 or entoderm, depending upon the species, or lie in 

 the mesoglea. We know that external conditions 

 may stimulate reproductive activity in certain 

 ccelenterates (Frischholz, 1909) and consequently 

 the development of germ cells, and we must conclude 

 that these germ cells are present at all times in a 



