1890.] [Ryder. 



logical activities of the parent organism modified or swayed toward male- 

 ness or femaleness, through some series of correlated influences which are 

 self-regulated in some way through nutrition, in the struggle of the parts 

 of the parent organism with each other for their allotment of nutriment. 



So far, the evidence tends to indicate that the egg is a repressed condi- 

 tion of maleness. That is, the high anabolic condition of the male ele- 

 ment is the consequence of unimpeded growth resulting in rapid segmen- 

 tation, while the female element is in some respects katabolic with an 

 unimpeded growth of its cytoplasinic constituents accompanied by a* 

 repression of the capacity for segmentation. 



The peculiar conditions of growth of the egg, and its usual trait of 

 great size, constitute probably the real essence of the meaning of sex, as 

 a means of favoring, in an increased ratio, the survival of offspring. 



The preponderance in the actual volume of the chromatin of the egg, 

 over that of the spermatozoon, expresses a physiological differentiation 

 not reached by the latter so much more quickly matured. This might be 

 due to the fact that the cytoplasm in the male element is smaller in amount 

 than that of the egg, and may be coordinated or physiologically con- 

 trolled by less chromatiu. On such a basis the hypothesis of Minot and 

 Balfour might be rehabilitated in part, but not on the erroneous basis of 

 sexuality as they supposed, but upon the far more significant one of physio- 

 logical differentiation or division of labor. 



Maleness is characterized, in the male element, by the absence of a 

 cytoplasinic field in which nuclear motion or karyokinesis can occur. 

 With this in the male element goes an inability, after sexuality is fully 

 established, to maintain further nutrition and growth without the help of 

 the female element. 



Femaleness, on the other hand, is characterized by the presence of an 

 enormous cytoplasmic field in the midst of which there is -placed a large 

 nuclear body containing proportionally to its envelope of cytoplasm a very 

 small amount of chromatin. Such a germ is incapable, except under the 

 antecedent stimulus of exceedingly vigorous processes of growth, as in 

 the case of parthenogenesis, of spontaneously beginning and maintaining 

 an orderly process of karyokinetic movement leading to further metabol- 

 ism growth and development, unless "fertilized " or fused with the male 

 element. 



The tendency in the male cell is towards a preponderance of chromatin, 

 in the female cell towards a preponderance of cytoplasm. The elabora- 

 tion of the chromatin in the male clearly takes place in some cases at the 

 expense of cytoplasm ; the elaboration of cytoplasm in the female is pos- 

 sibly at the expense of chromatin, and certainly at the expense of the pro- 

 longed exercise of the function of the latter as an essential part of the egg 

 nucleus. 



These processes in the two sexes admit of further contrasts. The cyto- 

 plasm is mobile and amoeboid and the immediate instrument of intussus- 

 ception of new material. The chromatin, on the other hand, while 



PROC. AMER. PHILOS. SOC. XXVIII. 132. P. PRINTED MAY 24, 1890. 



