DEGENERATIONS, DESMOGNATHUS 241 



ill illustration of the synizesis figure in Desmognathus. The 

 limitation of synizesis to this period of the year is not due to the 

 fact that at this time the ''testis contains relatively more cells 

 in this particular stage of development" as has been intimated 

 might be the case (King, '07). To appreciate this it is necessary 

 to keep in mind the 'polarity' of the urodele testis which permits 

 a very exact location of given stages and determination of their 

 sequence. Thus the examination of longitudinal sections of 

 organs secured throughout the spring shows in each a succession 

 of cysts filled with cells in stages grading from the spermatogonia 

 to mature and dividing spermatocytes. As has been said, it is 

 only after the 'boundary' limiting that season's production is 

 well marked that definite instances of synizesis a'ppear — unless 

 indeed, the isolated cysts of cells with markedly contracted nuclei 

 that are found in testes from the spring months before the 

 boundary plane appears represent synizesis. In this event, the 

 cells recover and are not degeneration figures. 



As far as synapsis (.syndesis) or the 'conjugation of the chro- 

 mosomes' is concerned, it appears to be lacking in Desmognathus. 

 We have carefully reexamined the question in extensive material 

 and fail to find any indication of a fusion of the chromosomes, 

 parallel or end to end, or, indeed, of a splitting of the chromatin 

 threads in the early growth period of the spermatocyte. The 

 splitting of the chromosomes of the spermatocyte I in preparation 

 for the first division appears quite early; but it becomes more and 

 more distinct and complete as the division is approached. The 

 changes of the growth period of the spermatocyte I occur essen- 

 tially as already described by Kingsbury ('02). 



Whatever general agreement may be ultimately reached as to 

 the facts, i.e., the general occurrence of a union in the spermato- 

 cyte (or spermatogonia! anaphase) of distinct chromosomes, end 

 to end or parallel, and the prevalence of a contracted condition 

 of the nuclear contents — the explanation of the phenomena re- 

 mains quite distinct, nor should it be confounded with whatever 

 teleological significance may attach thereto. Thus such an hy- 

 pothesis as the abortive mitosis interpretation of the synapsis 

 period by R. Hertwig seems particularly suggestive, since it pre- 



