B. F. Kingsbury 119 



The life of the spermatocyte of the second order must be short, very 

 short as compared with the gi'owth period of the spermatocyte of the 

 first order and the transformation period of the spermatid, since never 

 at any time do more than a few lobules contain spermatocytes of the 

 second order. In size these are markedly smaller than the spermatocytes 

 of the first order, and during their existence do not show an appreciable 

 increase in size. The chromosomes remain distinct throughout, never 

 losing their individuality, though a nuclear membrane is formed with 

 a development of linin. 



General Considerations. 



In the brief discussion just given of the divisions of the spermatocyte, 

 questions of their interpretation as mitoses have been entirely ignored. 

 While sutScient attention has not been devoted to the study of the 

 " mechanics " of the divisions, a word may be vouchsafed on certain 

 points. Any contribution offering correct or suggestive interpretations 

 in this most difficult field must, at the present time, be the result of 

 comparative work, and that I have not done in this case. My aim has 

 been, therefore, to keep the analysis of cell and nuclear structure as 

 simple as possible, ensuring only its being sufficient for the purposes of 

 this paper. Eisen's more elaborate analyses of granosphere, plasmo- 

 sphere, hyalosphere and cone-fibers, were not found applicable in 

 Desmognathus; they are felt to be premature. The purely mechanical 

 interpretation of the processes of division given by Eisen (and others), 

 I cannot consider at all satisfactory, nor can his statement that " the 

 mitosis of the cells of the testis of Batrachoseps is the result of two 

 independent parallel processes cooperating only at certain points," receive 

 my confirmation from the study of the same divisions in Desmognathus. 

 In the maturing spermatocyte of the first order, the arrangement of the 

 developing chromosomes with their free ends toward the idiozome, 

 suggests an interaction of the two during this period, and the idiozome 

 as the metabolic center of the cell-body. As has been said, if Flem- 

 ming's fluid is employed instead of Hermann's fluid, there is revealed 

 a massing of substance about the idiozome not indicated by the other 

 fixer — quite possibly soluble proteids. The loss of orientation when 

 growth is attained, the splitting of the chromosomes followed by the 

 changes in the idiozome point, I believe, to an intimate interrelation 

 of the two sides of the phenomena. Meves, McGregor and Eisen have 

 assumed that the arrangement of the chromosomes on the spindle and 

 their subsequent migration axe due to a force of contractility in the 



