Evidence from Metazoan Germ-Cells 25 



volves morphological division of substance; sorting out of 

 functions implies sorting out of the material substratum 

 of functions." 



If cytoplasmic sorting out and localization as well in the 

 earliest as the latest stages of development constitute dif- 

 ferentiation "and hence heredity," how, one must ask, can 

 the hypothesis that "the chromosomes are the seat of the 

 inheritance material" ever "practically amount to a demon- 

 stration"? The only way, so far as I can see, to reconcile 

 these two statements is to say that in so far as the expres- 

 sion "seat of inheritance material" means anything, both 

 chromosomes and cytoplasm are such seats, and hence that 

 neither is the seat of it. 



But it is not enough to point out that there is contradic- 

 tion here. We must try to discover just how so careful a 

 reasoner as Conklin should fail to detect it, for we may 

 feel certain that the failure is due not to mere oversight or 

 carelessness but to some defectiveness in standpoint or gen- 

 eral mode of procedure. Conklin fully realizes, as our quo- 

 tations show, that movements of the cytoplasm go far to- 

 ward determining the attributes of the eggs of Ascidians 

 and many other animals. But the following makes the 

 recognition still more definite: "Undoubtedly the most im- 

 portant of all the localizing factors so far recognized are 

 cytoplasmic movements." 14 



Assuming that our contention is valid that these localiz- 

 ing factors of the cytoplasm are inheritance factors (and 

 the virtual admission of this by Conklin in one of the two 

 statements which we hold to be contradictory should be 

 noted) we have still to see by what facts and reasoning Conk- 

 lin reaches the view that his observations support the 

 theory that "chromosomes are the seat of inheritance mate- 

 rial." The observations in this case which support the 

 chromosome theory are that the three kinds of cytoplasm 

 of the egg: the yellow protoplasm (mesoplasm), the sphere 



