116 The Spermatogenesis of Desmognathiis Fiisca 



of the ends of the chromosomes varies widely. In some cases the fused 

 ends project prominently from the spindle in the equatorial plane, thus: 

 [^ Such forms occur more often in the short and broad spindles, 

 and it is believed represent an extreme expression of a tendency of the 

 chromosomes to fuse, made possible by different " mechanical " condi- 

 tions. 



The disappearance of the polar radiations as the spindle develops has 

 been commented upon hj McGregor and explained by Meves as due to 

 the absorption of their ends as the spindle grows. In Desmognathus the 

 polar radiations are possibly more marked in the metaphase, but rapidly 

 disappear in the anaphase. In the anaphase the migration of the 

 daughter-chromosomes and their secondary fission as they pass to the 

 poles occur in much the same way as described in other forms, Fig. 16. 

 The secondary longitudinal fission in Desmoganthus is shown in Fig. 15. 

 As the chromosomes approach the poles, they become so closely massed. 

 Fig. 17, that the individual outlines are completely lost. This massing 

 serves to completely mask the secondary splitting that in the early 

 anaphase is evident. The centrosomes pass to the extreme periphery 

 of the cell and become no longer recognizable, so that I was unable to 

 identify them and trace them continuously to the division of the sperma- 

 tocyte of the second order. A well-defined astral shield was not recog- 

 nized in Desmognathus, nor was there any indication of a migration of 

 the centrosomes, such as both Meves and McGregor have found in the 

 forms studied by them. The vacuole on the polar side of the chromatin 

 mass, which in Salamandra occurs under the astral shield, is, however, 

 present. 



The mid-body and the remains of the central spindle present the same 

 characteristic appearances already well known in other forms, as may 

 be judged from Fig, 17. No attention has been devoted to their mean- 

 ing and fate. 



The Second Division. — The chromosomes in the telophase of the 

 division of the spermatocyte of the first order are closely massed in an 

 apparently structureless mass, much contracted. When the chromatin 

 expands to form the nucleus of the spermatocyte of the second order, 

 the chromosomes separate from each other, and it is then seen that they 

 occilpy the same position as in the late anaphase of the previous division; 

 their apices are turned toward the former pole of the spindle, and the 

 branches of the Vs extend back toward the opposite pole. Fig. 19. This 

 is, of course, of typical occurrence and needs no emphasis. The chromo- 

 somes, are, however, seen to be double, so that from the apex of each, 

 where they are united, four chromatin threads radiate out. Fig. 20 



