138 ROBERT CHAMBERS, JR. 



Fig. 3, e and /, show the primary spermatocyte in metaphase 

 and telophase. The chromosomes then pass into an interkinetic 

 resting nucleus, Fig. 3, g. The resolution of the chromosomes 

 of the two daughter cells into a resting nucleus is not always 

 synchronous. One may often find an interkinetic nucleus at one 

 end of the telophasic spindle while the chromosomes at the other 

 end are still massed in a densely staining body. There is no- 

 doubt, however, that both ends pass into the resting state and 

 form normal nuclei for one may find the entire contents of an 

 island in interkinesis. And in still older islands all the cells 

 pass into Metaphase II., leaving no cells behind. Fig. 3, h, repre- 

 sents the nucleus of a secondary spermatocyte in prophase. The 

 chromosomes are approximately eight in number. They are 

 shown in Fig. 3, i, in metaphase. Fig. 3, k-o, show the cellular 

 elements lying in part of the lumen of a maturing testis and a 

 portion of the adjacent wall. The secondary spermatocytes, 

 Fig. 3, k, are shown in telophase. At / are spermatids with 

 vesicular nuclei. Their arrangement in islands is better shown 

 in the upper part of Fig. 2. Upon the disintegration of the 

 surrounding cytoplasm, the spermatids come to lie in the lumen 

 of the testis. Here, Fig. 3, m, the nuclei contract somewhat and 

 become more densely chromatic. 



In some of the spermalids, Fig. 3, n, n, the contents of the 

 nucleus collects into a compact eccentric mass, which finally 

 disintegrates and disappears. 



In other spermatids the nucleus remains vesicular and it is 

 this second type only that is to be found in the distal end of the 

 vas deferens of a mature testis. 



That approximately half of the spermatids degenerate is the 

 impression gained by the examination of sagittal sections of 

 entire testes. 



Lepeschkin, 1 in a brief paper in Russian, kindly translated 

 for me by Dr. M. Scholtz, of Cincinnati, on the spermato- 

 genesis of the Daphnid, Moina rectirostris, describes occasional 

 degenerating cells not only among spermatids but also among 

 spermatocytes and spermatogonia. He speaks of the uniformity 



1 W. D. Lepeschkin, Mem. Soc. Amis Sc. Nat. Anthrop. Ethnogr. Univ. Moscon, 

 Vol. 98, Sect. Zool., Vol. 3, No. 9, 1907. 



