128 The Spermatogenesis of Desmognathus Fusca 



fusion of the daughter-chromosomes inter se is not so marked, though 

 in certain cases it seems to be exhibited; e. g., in Anasa, Paulmier, gg. 



The significance of this tendency toward fusion and its cause are, of 

 course, obscure. Possibly it is due in part to a more labile condition 

 of the chromatin in the spermatocyte, which would cause the chromo- 

 somes to run together and round off whenever other forces permitted 

 and in a corresponding manner and degree. This marked lability is 

 indicated by a number of facts that appeal to one in studying the 

 divisions in a particular form, as well as in examining the published 

 figures of the conditions in other forms: the strong tendency of the 

 chromosomes to mass together as they approach the poles of the spindle 

 in the anaphase; the great irregularity of the forms of chromosomes 

 presented; and the readiness with which they change shape. Typical 

 tetrad-formation itself may be in part the expression of this same ten- 

 dency of the chromatin to round off, due to a more fluid consistency. 



Whatever the factors upon which the ring and cross formations de- 

 pend, it is my belief that they cannot be interpreted apart from the 

 entire problem of cell division. I fully appreciate that no real explana- 

 tion is offered in what has been written above; nor is it meant as a 

 criticism of the excellent work done upon spermatogenesis and oogenesis. 

 Those investigations in which the spermatocyte divisions have been 

 studied as mitoses are also recognized. I simply present my view as 

 to the standpoint from which the phenomena of spermatogenesis should 

 be considered in order that a firmer basis be given for interpretation; 

 that view is, — that the divisions be studied as such, and the case and 

 effect of the omission of the second growth period be sought; that the 

 chromatin changes be considered from the standpoint of chromatin 

 changes elsewhere and as a part of the entire phenomenon of cell 

 division. 



If we return again to a consideration of Desmognathus, we find in the 

 first mitosis, ring-formation, usually quite irregular and variable; in the 

 second division, cross-formation. In the first division it is the ends of 

 the chromosomes that show the fusion more strongly, and rings result; 

 in the second division their middle points (the apices of the V's) fuse 

 and X's result, the behavior of the daughter-chromosomes of the two 

 divisions in this respect being antithetic, a condition that may have 

 significance and which occurs also in other forms (v. Klinckowstrom, 

 van der Stricht, Ishikaua). If we consider the chromosomes in the two 

 spermatocytes in their relation to the pole of the cell (centrosome), in 

 the growing spermatocyte, the chromosomes form loops with their ends 

 toward the centrosomes; in the spermatocyte of the second order, the 



