122 The Spermatogenesis of Desmognathus Fusca 



formation occurs. The second (axial) splitting may be postponed and 

 occur in the anaphase as ihe chromosomes are passing to the poles. 

 The figures strongly suggest that there is a close resemblance to the 

 divisions in the spermatogenesis of Desmognathus, modified by the more 

 rapid succession of the division in the polar-body formation. 



From these comparisons there seems little doubt as to the interpreta- 

 tion of the second division in Desmognathus as a longitudinal splitting, 

 nor as to its being the persistent longitudinal splitting which occurred 

 in the anaphase of the first division. The second splitting in Flem- 

 ming's heterotypic mitosis is clearly, then, the precocious division of the 

 chromosomes for the succeeding division, and should not be considered 

 an essential character of heterotypic division, since it would not neces- 

 sarily occur, I believe that Amphiuma agrees with Desmognathus in 

 this respect. The interpretations of Carnoy and Le Brun are unique, 

 and cannot be reconciled with my own findings. 



It is not necessary here to refer in detail to the influence Weismann's 

 theory of the germ-plasm has had upon spermatogenesis work. Practi- 

 cally the only detailed work that had appeared prior to his first publica- 

 tion, in 1887, touching on the question of a reduction was Flemming's 

 classical paper upon the divisions of the spermatocyte in Salamandra 

 maculosa. Under the stimulating influence of Weismann's essay, paper 

 after paper appeared — by Henking, vom Eath, Eiickert, Hacker and 

 others — some of which seemed to bring wonderful proof of the correct- 

 ness of his prophecy, while in other cases, as those of Brauer, Boveri, 

 Moore, Moves, etc., the results were contradictory. 



Owing largely to Weismann's theory and its apparent confirmation, 

 there has been a powerful impetus given to the work in oogenesis, 

 spermatogenesis, fertilization and cleavage, and from the standpoint 

 of his brilliant theory new possibilities of interpretation of the phenom- 

 ena of development have been brought out in testing its accuracy. In 

 so far as it has led to these results, much could be said of the beneficial 

 influence " Weismannism " has had in biology. On the other hand, in 

 the investigation of oogenesis and spermatogenesis, the study of the 

 phenomena has been made too largely a search for the occurrence of 

 tetrad-formation and reducing divisions. An unproved theory, a specu- 

 lation, highly suggestive and stimulating, but altogether hypothetical 

 and not admitting of even partial proof, has been made the basis of the 

 work, and it has diverted attention from other points of view that would 

 have given a more normal, though perhaps not so rapid, development of 

 this field of work. 



A truer basis upon which an interpretation of the phenomena of 



