Ryder.] 1"" [May 16, 



corresponding greater specialization and differentiation than that of the 

 spermatozoon . 



This view then satisfactorily accounts for the expulsion of the polar 

 bodies and also gives some indication of the significance of the reduction 

 of the cytoplasm of the spermatozoon or its complete loss, if we regard 

 the egg and spermatozoon as antipodal expressions of a physiological pro- 

 cess of evolution, which has resulted in forming bodies which are comple- 

 mentary to each other in every physiological trait which they present. 



Since spermatozoa, also, are very often produced from what are mani- 

 festly ova, by the breaking down of the latter and the augmentation of 

 their chromatin, it is clear that the spermatic body is a product derived 

 from the egg by carrying its cleavage farther either by means of the 

 direct or indirect method, but while still attached to the parent or nour- 

 ished by it. From this consideration it follows that the egg and spermatic 

 body are not homologues before the final maturation of the former. It 

 is, therefore, useless to expect to find any structures thrown off by 

 spermatozoa which are complementary, in the sense implied by Minot 

 and others, to the polar bodies of the egg. 



As I have been led to the views expressed above by following a totally 

 different path from Weismann, and as I reject his hypothesis of the phj'si- 

 ological isolation of the germ-plasm on the basis of fact, as shown else- 

 where,* as incapable alike of proof or of serving a better purpose than a 

 much simpler hypothesis, it seemed best to continue the argument upon 

 the lines begun in earlier papers. 



It may, however, be well to point out here that what Weismann means 

 by his " histogenetic " or "ovogenetic/' nucleoplasm, I distinctly limit 

 to the genesis of the huge cytoplasmic field or cytoplasm and yolk of the 

 ovum. The egg membranes are basement membranes and it is difficult to 

 say what share the egg had in their formation except in lower forms, so 

 that they are of far less consequence in this discussion than Weismann 

 supposes. 



Another point is that parthenogenetic ova are certainly smaller than the 

 fertilized ova of the same species, in some forms, though this is not 

 always the case. This fact, however, is in accord with the hypothesis of 

 the polar bodies set forth above. The mode of feeding the queen bee \ 

 shows, also, that parthenogenetic eggs, or those capable of developing in that 

 way, are probably produced through the expenditure of less energy in the 

 parent organism than those which develop only in the sexual way in 

 strictly sexual forms. The connection of these facts with the explanation 

 offered of the expulsion of the polar bodies is so obvious that it hardly 

 needs to be indicated. 



It has been made clear that the overgrowth of the egg has resulted in its 

 specialization, but the question still remains, What led to such an over- 



*"A Physiological Hypothesis of Heredity and Variation." American Naturalist, pp. 

 85-92, xxiv, 1890. 

 t Cheshire, " Bees and Bee Keeping," Vol. i, pp. 82-85. 



