Ryder.] \2i2i [May 16, 



appearing to centrally control this process, is never immediately, but only 

 mediately involved in its execution. No cases are recorded where the 

 chromatin shares directly or immediately in the process of digestion or in- 

 tussusception of new matter, except possibly the Bacteria or Schizomy- 

 cetes. 



The female cell previous to final maturity has been involved in the ac- 

 cumulation of the cytoplasm ; in this process its chromatin has been indi- 

 rectly involved and has increased in volume proportionally. This same 

 fact is illustrated in the increased dimensions and complexity of the nu- 

 cleus as growth in cytoplasmic dimensions increases in even such simple 

 forms as Amoeba, as may be clearly seen in Leidy's monograph upon the 

 Rhizopods of North America, where the changes in the relative proportions 

 and arrangement of these substances are fully illustrated in the progress 

 from the young to the adolescent stages. 



There is therefore ground for the belief that there is a certain minimal 

 proportion of chromatin necessary for every cell which is necessary to 

 maintain its physiological integrity. In the egg cell the chromatin must 

 share in the constructive metabolism involved in the prolonged growth 

 necessary to mature the ovum. It is not improbable that this function of 

 sharing in constructive metabolism and not in that of karyokinesis has 

 rendered the egg incapable of spontaneous segmentation, unless it be the 

 product of a tremendous energy of growtli and conditions of assimilation, 

 as in the case of parthenogenetic ova. 



Not only the chromatin, but also the whole of the rest of the nucleo- 

 plasm of the egg, is probably, like that of any other physiological differ- 

 entiated cell of the parent body thus rendered in most cases incapable of 

 undergoing immediately the spontaneous changes necessary to cause the 

 beginning of development. 



The equilibration of forces leading to the growth of male and female 

 elements, respectively, in the parent organism is in some way self-ad- 

 justed or self- regulated. It is probably true that in many cases there is 

 good reason to assume that the eggs are more favorably situated in refer- 

 ence to supplies of nutriment than the spermatogonia, or conditions sub- 

 sist which tend to repress spermatogonial segmentation. 



Such a view may be fortified with a great host of facts drawn from the 

 relations of the male and female reproductive organs, in many forms, to 

 the sources of nutriment. In many cases the ovaries are clearly in a more 

 direct and favorable relation to the sources of supply of nutriment than 

 the testes, as in many Bryozoa, for example. Or the source of supply of 

 nutriment for the reproductive organs is more remote for the testes than 

 it is for the ovaries, as is actually the case in many forms, notably a large 

 proportion of mammals where a descensus testiculorum supervenes. Or, 

 in other cases, the surplus nutritive matters are competed for within the 

 organism by structures which are usually described as belonging to the 

 category of the secondary sexual characters. Or, in another very large 

 class of data, we have evidence tending to show that the ovum is placed 



