RECENT RESEARCHES ON SPERMATOGENESIS. 323 



lie corpuscle." This gradually enlarges until it has assumed 

 the shape and size of the head of the mature spermatozoon, 

 that is, more or less pear-shaped. At the same time, or directly 

 after, the tail of the spermatozoon appears in an unex])lained 

 manner in the substance of the spermatoblast, while the sper- 

 matoblastic nucleus disappears, so that the group of spermato- 

 blasts have given place to a bundle of spermatozoa united in a 

 bundle and supported on the " mother cell." The further 

 history concerns only the ** mother cell '^ and principal nucleus 

 (my blastophor) which, according to M. Duval's observations 

 and my own, undergoes fatty degeneration and disappears. 



M. Duval's next communication is contained in the * Rev. 

 de Science Nat.,' Sept., 1879, in which he gives an account of 

 the two kinds of spermatozoa which since the time of Von 

 Siebold have been known to be present in Paludina. This 

 paper need not detain us longer than to mention that he finds 

 that the two kinds of spermatozoa develop on the same plan 

 as those of the snail, and that they are veritably two different 

 kinds of spermatozoa, a fact which some naturalists have 

 disputed. 



The next publication from the pen of this writer is in the 

 'Rev. de Sci. Nat.,' Sept., 1880, on the " Spermatogenesis of 

 the Common Frog," which also formed part of the subject of 

 my second paper; and on comparing the two the similarity of 

 the figures are striking, though the interpretations drawn from 

 them are not quite in agreement. 



He commences his description by showing the condition 

 of a testicular crypt during the winter, when the spermatozoa 

 are seen to be united into bundles, which bundles are arranged 

 in a radial manner, with remarkable regularity around the 

 walls of the sac. The wall of the sac itself is formed of 

 fibrous tissue and cells, and of the latter two kinds can be dis- 

 tinguished, one the " male ovules," the other smaller and 

 more granular, embedded firmly among the male ovules, which 

 constitute the source from which the male ovules are derived. 

 This condition of things obtains throughout the winter till 

 the spring, when the spermatozoa are discharged and changes 



