davis: spermatogenesis. 79 



3. Growth Period of the Primary Spermatocytes. 



A. Dissosteira Carolina. 



1. Autosomes. 



Immediately'succeeding the telophase of the last spermatogonia! 

 division the chromatin becomes diffused throughout the nucleus in 

 the form of irregular granules suspended in the linin network (Plate 

 2. Fig. 26). At intervals the granules may be aggregated into clumps, 

 which are often of considerable size. This stage, which marks the 

 beginning of the primary spermatocytes, is, 1 believe, comparable to 

 the resting stage of the spermatogonia. 



For the sake of convenience in describing the history of the pri- 

 mary spermatoc}i;es it has seemed desirable to distinguish ten quite 

 well marked stages, of which the condition described above is the 

 first, or stage a. 



During the telophase of the last spermatogonia! division and the 

 earlv part of stage a the chromatin is often shrunken away from the 

 nuclear membrane forming a deeply staining mass eccentrically placed 

 within the nucleus (Figs. 24, 25). Such a condition e^'idently corre- 

 sponds to that first described by Moore ('95) to which he applied the 

 term "synapsis." Similar appearances have been described by a 

 number of later writers on spermatogenesis, but usually, there seems 

 to be more or less uncertainty as to whether this condition is normal. 

 At first I was inclined to believe that this is a normal stage which lasts 

 but a very short time, since cells in this condition occur quite commonly 

 during the late telophase and beginning of stage a, but at no other time. 

 However, a more careful study has con^inced me that such a condition 

 of the chromatin is, in reality, an artifact. I am led to this conclusion 

 more especially by the fact that in almost every case the cells of the 

 peripheral layer, which are in contact with the follicular wall and thus 

 in the most favorable position to be acted on promptly by the fixing 

 agent, show no such contraction of the chromatin. It is, however, 

 undoubtedly true that at this stage, and at no other, the chromatin 

 shows a marked tendency to contract away from the nuclear membrane 

 if not properly fixed. 



Stage a is quickly followed by stage b (Fig. 28), which is character- 

 ized by the collection of the chromatin into more or less definite, elong- 

 ated masses. These masses are connected with one another and with 

 the nuclear membrane by fine linin fibrils and have, in general, the 



