112 The Spermatogenesis of Desmoguatlius Fnsca 



being constructive and a fundamental phenomenon in the formation of 

 the spermatocyte, may be an expression of a " running out " in the 

 spermatogonium stock, and represent a tendency toward degeneration. 

 We know as yet too little of the occurrence of contraction-figures in 

 different forms to drav/ any general conclusions; possibly quite different 

 phenomena may be here included. The fact of their occurrence in 

 DesmognatJius only at the end of the season of spermatocyte-formation 

 is, I think, suggestive, and further knowledge of their presence in other 

 forms from this point of view is desirable. 



Groictli of the Spermatocyte. — The growth of the spermatocyte has 

 already been well described by Meves, 96, Herman, 89, and McGregor, 

 99, so that a detailed discussion is unnecessary. The chromatin of the 

 spermatogonium is irregularly distributed in the nucleus in the form 

 of an apparent network, Fig. 1. The changes in the nucleus are the 

 following: The chromatin in the form of small granules becomes more 

 evenly distributed in the nucleus upon the linin frame-work, which still 

 appears to be a close reticulum with the chromatin evenly distributed. 

 Gradually, the chromatin is concentrated in the form of a thread (or 

 threads) connected by the linin network. It is at first hard to say 

 whether a single thread or several (twelve) threads are so formed. Soon, 

 however. Fig. 2, the free ends of threads are discernible projecting from 

 the tangled mass on the side toward the idiozome. From this time on, 

 in the growth of the spermatocyte, the chromatin threads or cliromo- 

 somes shorten relatively and increase in thickness. Fig. 3; they may 

 now be counted and are found to be twelve in number. Their free ends, 

 typically at least, are toward the idiozome (see Montgomery, 00, p. 352), 

 so that they form a more or less irregular horseshoe. They are made 

 up of a succession of numerous and large chromatin granules connected 

 together by a less chromatic substance, giving the characteristic beaded 

 appearance shown by Hermann, and now so well known. They are not 

 smooth but possess processes joining the linin network of the nucleus 

 and giving to the thread (chromosome) a fanciful resemblance to a string 

 of daisies, as has been said by others. 



The establishment of the spirem from the resting nucleus of the sper- 

 matogonium, and the shortening and thickening of the chromatin 

 threads, are but a part of one continuous process of growth, so I have 

 considered them together rather than as belonging in part to the suc- 

 ceeding division. The process is one involving a considerable period 

 of time, as judged from the large number of lobules containing growing 

 spermatocytes in various stages of development. During this period, 

 there is a steady increase in the size of the nucleus, as may be seen from 



