156 H. H. Nezvman 



of the egg protoplasm. This point of view has been clearly ex- 

 pressed by one of its leading exponents'* in the following words: 



"Finally as evidence that inheritance may take place through 

 the cytoplasm ot the egg, reference must be made to the extremely 

 important work of Loeb and Godlewski. By concentration of 

 hydroxyl-ions Loeb found that it was possible to cause the sperma- 

 tozoa of starfishes and ophiurans to fertilize the eggs of sea- 

 urchins. The embryos and larvae resulting from such crosses 

 showed only the characteristics of the mother. Later Godlewski, 

 using the same methods, was able to fertilize the eggs ot a sea- 

 urchin with the sperm of a crinoid, and although such hybrids were 

 raised to the larval stage, they showed only maternal character- 

 istics. Still more, enucleated urchins eggs fertilized by crinoid 

 sperm produced gastrulae of purely urchin type. These results 

 demonstrate, as Boveri admits, that the chromosomes 01 the 

 sperm do not in this case influence or modify the cytoplasm of the 

 egg cell; while the experiments on the enucleated egg show that 

 the characteristics of the organism, at least as late as the gastrula 

 stage, are derived entirely from the egg cytoplasm. 



"Boveri long since showed that the early stages of development, 

 perhaps as late as the blastula or gastrula, are uninfluenced by the 

 spermatozoon and are purely maternal in type; in the case of God- 

 lewski's hybrid larvae, he supposes that the sperm chromosomes 

 remain permanently inactive. But however this result is to be 

 explained, it may be considered as definitely settled that the early 

 development of animals is of purely maternal type, and that it is 

 only in stages later than the gastrula, and consequently after the 

 broad outlines of development and the general type of differen- 

 tiation have been established, that the influence of the sper- 

 matozoon begins to make itself felt; and it is equally certain that 

 this type of differentiation is predetermined in the cytoplasm of 

 the mature egg cell, rather than in the egg nucleus. 



"On the other hand, there is no doubt that the differentia- 

 tions of the egg cytoplasm have arisen, in the main, during the 

 ovarian history of the egg, and as a result of the interaction of 



* Conklin, E. G. Science, N. S., vol. zy, no. 168, p. 98. 



