100 The Spermatogenesis of Desmognathus Fusca 



which appeared iu 1887, is classical, not only as a contribution to tlie 

 knowledge of spermatogenesis, but of mitoses in general. In Salamandra 

 Flemming recognized the period of multiplication of the spermatogonia, 

 followed by the period of growth to form the spermatocyte, which he be- 

 lieved divided twice, forming medium-sized and then small cells. The 

 latter he apparently thought divided again,^ there being thus three gener- 

 ations of cells resulting from the division of the si3ermatocytes. In these 

 divisions were recognized and named two divergent types of mitosis, 

 " homotypic " and " heterotypic " — terms and types widely known in 

 spermatogenesis work. The divisions of the spermatogonia were found 

 to be homotypic, those of the spermatocyte of the first order character- 

 istically heterotypic, though homotypic divisions also occurred; the 

 division of the spermatocyte of the second order was believed to be 

 heterotypic and homotypic equally. 



In the interval between the appearance of Flemming-^s paper, 87, and 

 vom Eath's, 93, Weismann, 91, had published his prophecy that in the 

 process of spermatogenesis and oogenesis a " reducing " division would 

 be found to take place. 



The results of Haecker, Henking, Eiickert and vom Eath appearing 

 soon after, brought an apparent confirmation of the correctness of this 

 prediction, in the forms investigated by them. Yom Eath approached 

 the investigation of Amphibian spermatogenesis (Eana, Salamandra) 

 fresh from his results in Gryllotalpa, in which he had described tetrad 

 formation. To the three generations described by Flemming he added a 

 fourth in which tetrads were formed and which were distributed in two 

 more divisions, as he believed to be typically the case, making six gener- 

 ations in all. Vom Eath's investigation was evidently undertaken to see 

 if tetrad formation did not also obtain in Airiphibia, and he was led to 

 suspect the correctness of this view by certain descriptions and figures 

 'of Flemming in which tetrad formation was apparently shown, though 

 regarded as abnormal. 



Moves' published work on the spermatogenesis of Salamandra began 

 in 1891, his main paper appeared in 1897, followed the next year by a 

 paper on the transformation of the spermatid into the ripe spermatozoon. 



2 The statements of Flemming on this point do not seem to leave his interpretation 

 entirely clear. In his schematic table of the cell generations, only two generations 

 are given as descendants of the spermatocyte, and the following words convey the 

 same impression " Mehr Tochtergenerationen der grossen Zellen als zwei scheinen 

 mir den vorlindlichen Zellengrossen, nicht vorzukommen" (p. 401). Nevertheless, to 

 Meves, Flemming personally stated that he had believed there were three generations 

 of cells. 



