PROMORPHOLOGICAL RELATIOXS OF CLEAVAGE 



385 



take sufficient account of the fact that development does not nec- 

 essarily begin with fertilization or cleavage, but may begin at a far 

 earlier period during ovarian life. As far as the visible promorpho- 

 logical features of the ovum are concerned, this conclusion is beyond 

 question. The only question that has any meaning is whether these 

 visible characters are merely the expression of a more subtle pre- 



Fig. 181. — Variations in the axial relations of the eggs of Cyclops. From sections of the eggs 

 as they lie in the oviduct. [Hacker.] 



A. Group of eggs showing variations in relative position of the polar spindles and the sperm- 

 nucleus (the latter black) ; in a the sperm-nucleus is opposite to the polar spindle, in b, near it or 

 at the side. B. Group showing variations in the axis of first cleavage with reference to the polar 

 bodies (the latter black) ; a, b, and c show three different positions. 



existing invisible, organization of the same kind. I do not believe 

 that this question can be answered in the affirmative save by the 

 trite and, from this point of view, barren statement that every effect 

 must have its preexisting cause. That the e^gg possesses no fixed 

 and predetermined cytoplasmic localization with reference to the 

 adult parts, has, I think, been demonstrated through the remarkable 



2C 



