310 GEORGE W. BARTELMEZ 



when it is borne in mind that the blastodisc from which the 

 embryo arises is differentiated under the direct influence of the 

 germinal vesicle. 



The fact that in the pigeon the polar axis persists unchanged 

 throughout the growth period of the oocyte, and the fact that 

 there is a polar axis in the earliest stages of the germ cells of all 

 vertebrates which have been described, indicate that the polar 

 axis persists unmodified from generation to generation in the 

 vertebrates and is one of the fundamental features of the organ- 

 ization of the protoplasm. The facts here presented may be 

 taken as evidence that bilaterality appearing as early as it does 

 in development, is likewise an expression of a fundamental char- 

 acter of the protoplasm. 



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