128 ON THE SPERMATOGENESIS OF THE SILK-WORM. 



periode " of German authors), the third the ripening stage 

 (" Reifungsperiode ") and the fourth the stage of metamorphosis 

 (" Umwandlungsperiode "). The cells of the first stage will be 

 called the primary germ-cells (Ursamenzellen), the cells of the 

 second stage, the spcrm-mother-cclls after O. Hertwig. The cells 

 which divide two times successively in the ripening stage, 

 may be called the sperm-daugliter-celh. This sperm-daughter- 

 cell changes itself into a spermatozoon without further division. 



The Development of the Genital Elements. 



On examining a testis of a larva after the fourth moult, 

 we are struck with the varieties of cellular elements found in it. 

 As in the genital follicles of other Lepidoptera, the more 

 developed elements always lie near the vas deferens, while the 

 younger ones lie near the blind end of the follicle. In the 

 centre of the younger elements, near the blind end of each 

 testicular follicle, we find a large cell around which these 

 younger elements are arranged concentrically (fig. 7). 



Before passing to a description of the development of the 

 genital elements, I shall say a few words as to the nature 

 of this large cell in the blind end, which I shall call 

 " Verson's cell." As Verson has already worked over the 

 spermatogenesis of the silk-worm and described in two papers, 

 " la spermatogenesi nel Bombyx mori ; Padova, 1889," and 

 "Zur Spermatogenesis" in the Zoologischer Anzeiger, it is 

 necessary to quote here his opinion about this large cell. 

 His interpretation of it, as is given in the latter of these 

 works, is as follows : 



" In jedem Fache befindet sich nur eine einzige, grosse 

 Keimzelle ; und aus dieser nehmen nach und nach alle or- 

 ganisirten Bildungen ihren Ursprung, aus welchen der Inhalt 

 des ganzen Faches besteht." 



Let us now see whether this interpretation of Verson corres- 

 ponds with my observations or not. 



In the embryonic stage of the silk-worm, each testis 

 consists of only one follicle (Fig. 4) within which are scattered 

 round cells with distinct chromosomes and a nucleolus. 



