1890.] 1^ {Ryder. 



under conditions of growth, or is encapsuled within a porous basement 

 membrane — the zona radiata — so as to favor from every point on its sur- 

 face its cumulative growth in bulk, rather than its cleavage or segmenta- 

 . tion within the parent, which would end in its breaking up into male ele- 

 ments. The male elements, on the other hand, are not encapsuled, at 

 least in a very large proportion of cases, and are free to grow in another 

 way without an intracapsular repression of karyokinetic processes. It 

 would be an easy matter to cite multitudes of facts in support of the argu- 

 ment here offered, though I am aware that strong counter-arguments 

 might be produced, yet I do not believe that they are anything like as 

 weighty as the affirmative evidence. 



Again, all the facts tend to prove that the recurrence of male forms in 

 parthenogenetic types is associated with a decrease of the supply of nutri- 

 ment and a slight lowering of temperature. 



How do these facts comport with the data in our possession respecting 

 the manner of development of the characteristic male plasma or chro- 

 matin '? We find that after a certain limit of size has been attained by the 

 egg or spermatogonium in Ostrea edulis that the evolution of chromatin 

 begins and with this process the production and freeing of spermatozoa. 

 It looks as if the chromatin or characteristically male plasma required a 

 longer time for its elaboration than the cytoplasm, which is in consonance 

 with fact. In other words chromatin can be formed only from previously 

 elaborated cytoplasm, and the latter when its sources of nutriment are 

 cut off or diminished tends, in virtue of its freedom from any functional 

 dutj r in the parent body to be built up into a still more complex molecu- 

 lar form, as chromatin. Or the struggle of cells in the gonads for nutri- 

 ment may tend towards the male condition- provided all take part, and 

 spermatozoa result ; if only a few take part in the struggle, under encap- 

 suled or other conditions unfavorable to the elaboration of chromatin and 

 knryokinesis, the female or large celled type of germ is formed. 



That something of this nature must occur is evident if we contemplate 

 the problem from the purely morphological side, but with the physiologi- 

 cal aspect of the matter still in view. The chromatin is primitively the 

 most central element of the plasmic contents of the cell. It is the most 

 homogeneous of all cell contents ; it is least like an emulsion of any of 

 the cellular constituents. In that it is the most distantly removed from the 

 periphery of all the cell-contents and the latest to appear when developed 

 in great quantity from the nuclei of egg-like spermatogonia, it is the 

 highest and latest product of cellular metabolism. It is therefore clear 

 that the element of time is to be considered, and that chromatin or the 

 most characteristic plasmic basis of the male element is the end-product 

 of the untrammeled exhibition of the energies of functionless or sexual 

 protoplasm. It is upon this ground that it is safe to assume that the male 

 element is the primary one and that the female element is secondary and 

 has arisen through a repression of the processes which lead to the meta- 

 morphosis of cytoplasm into chromatin. The male state is therefore the 



