B. F. Kingsbury 111 



The observations of the investigators enumerated would indicate that 

 the massed condition of the chromatin at the beginning of the growtli 

 period of the spore or sperm mother-cell is a natural phenomenon of 

 general occurrence without affording any clue to its significance; on the 

 other hand, the fact that careful investigations in spermatogenesis have 

 been made without noting the occurrence of any such phenomenon, sug- 

 gests that it is not of universal occurrence. 



In Desmognathus, the contracted condition of the nucleus at the be- 

 ginning of the growth period does occur, as was noted in my preliminary 

 publication, and it was then assumed to be of constant occurrence in the 

 spermatic cycle of this form. Subsequent and more careful study of 

 the form makes this seem very doubtful. Spermatocytes are being 

 formed during the fall, winter and spring, though growth in the winter 

 is probably slow, and transformation ceases to take place at about the 

 beginning of summer, as has been already stated. During this time 

 contraction figures are found rarely, and it is not until late May or June, 

 or in other words, in the last generations' ot spermatocytes, that contrac- 

 tion of the chromatin into a mass is general. The appearances so pro- 

 duced are quite similar to those found by Moore, Paulmier, Wiegand 

 and others, and are, I think, the same phenomenon; the chromatin 

 gathers at one side of the nucleus, leaving a space within the nuclear 

 membrane, with which it remains connected by a few shreds of linin. 

 At this time the chromatin is closely massed together and details of 

 structure are diflieult to make out, Fig. 18. There is no indication that 

 anything is cast out from the nucleus at this time, as Wiegand found. 

 With other workers, I feel confident that it is not an artifact, though 

 no examination of fresh tissue was made. The fact that it occurs only 

 at the end of the season of transformation at a time when the process 

 is almost ready to stop, dissociates it, I think, from the process of 

 " synapsis " or reduction. 



At about this time there begin to appear in the last generations of 

 spermatogonia contraction-figures which are essentially similar to those 

 described above, in which the contraction is excessive. In these, the 

 nucleus gathers into an apparently perfectly homogeneous round mass, 

 the chromatin often separating from it as though " squeezed out." 

 Such contraction-figures become abundant during July and August and 

 are clearly, I think, degeneration changes associated with the cessation 

 of transformation into spermatocytes, whether as cause or effect need 

 not be considered here. Further study of this interesting phase will 

 be undertaken in connection with the spermatogonia. 



It is suggested, therefore, that the contraction-figures, instead of 



