Ryder.] [May 16, 



this exemption of the germ-cells from the disintegrating effects of active 

 or functional metabolism which has given the first impulse to the accumu- 

 lation of yolk and the overgrowth of the spermatogonia, ending in the 

 production of the ovum and the essentially female condition. The apical 

 position in many plants of the female germ is significant in this connec- 

 tion, no less than the fact observed by Mr. Meehan, that in conifers the 

 female flowers are produced at the apex of the tree and by the most vig- 

 orous shoots. 



THE ORIGIN OP KARYOKINESIS, THE SIGNIFICANCE OP THE POLAR 



BODIES, VARIABILITY, SEXUAL PASSION AND SEX IN RELATION 



TO THE GENESIS OP SPECIES. 



It is a remarkable fact that in the lowest forms of life no evidence of 

 karyokinetic changes has ever been noticed. Spores are produced within 

 the body of the parent individual by the direct fragmentation of the 

 slightly more chromatophilous or deeply staining portion of the parent 

 plasma that fills nearly the whole of the latter, so that it is still not possi- 

 ble to speak of a nucleus in contradistinction to a cell-body of cytoplasm 

 in these organisms. These facts tend to show that in such very low forms 

 there is still a want of mobility of the plasma itself as well as a lack ot 

 differentiation into nuclear and cytoplasmic matter.* Is or is not the 

 want of a differentiation of cytoplasm associated with the absence of 

 karyokinetic phenomena ? There is much reason to assume that it is from 

 the consideration of a great variety of facts, mainly those observed in 

 the earlier stages of development of higher sexually produced forms. 



The main argument in favor of such a view is the circumstance which 

 has fallen under the eyes of every investigator, that the karyokinetic phe- 

 nomena are most pronounced in the earlier stages and on a larger scale 

 than in the later stages when the cells become smaller. This is either 

 associated with a larger proportional amount of cytoplasm or it is inde- 

 pendent of it. So far as observation has extended, the facts of early seg- 

 mentation tend to favor the first alternative of the foregoing proposition. 

 Another body of facts is equally favorable to such an interpretation, 

 namely, that of spermatogenesis. It is true that many forms of spennato- 

 genesis are known where karyokinesis is maintained up to the time that 

 the spermatic elements are beginning to form, but there are many other 

 cases known where this is not the case and where during the later stages 

 of spermatogenesis leading to the fragmentation of the spermatogonia 

 there is no evidence of accompanying karyokinesis. These facts tend to 

 show that, with the gradual diminution of the amount of investing cyto- 



*DeBary, in his Lectures on Bacteria, affirms that a nucleus is wanting in the 

 Schizomycetes, and the only case where these forms have been known to exhibit amoe- 

 boid movements, so as to throw out processes, is that described by Prof. Samuel G. Dick- 

 son, of this city; at least I have been unable to find any other instances of the kind 

 described. There appears to be little cytoplasm in these forms, so that these organisms 

 correspond mainly to the nuclei of the cells of higher types. 



