22 



from the time when it is recognizable until after the copulation of the 

 imago. 



From all these, we come to the conclusion that the single large cell 

 found in the blind end of each of the testicular follicles is not a germ 

 cell, as Ver s on states, but it corresponds rather to the supporting 

 cells of the testes of Vertebrates or the rhachis of the Ascaris egg-string 

 in its function. 



This supporting cell is not only present in the testes but also 

 occurs in the ovary of the silk worm. 



In other Lepidoptera such as the wild silkworm , Papilio xuthus, 

 lt., P. machaon, L., P. alcinous, Klug., I have found the similar large 

 cell in the blind end of the testicular follicle but not in Antlœrea ya- 

 ma mai, Guér. Mén., Caligura japonica,^looxe, Rhoclia fugax, Butl. etc. 

 From these facts , it seems evident that in the genital glands of Lepi- 

 doptera, this cell, although not constant, is not of rare occurance. 



In the testicular follicle of the silkworm, as in the genital follicles 

 of other Lepidoptera, the more developed sperm elements always lie 

 near the vas deferens , while the younger elements lie near the blind 

 end of the follicle round the central supporting cell. 



By this arrangement, we can find a series of various developmen- 

 tal stages, and in consequence of this we may distinguish various zo- 

 nes as van Beneden, O. Hertwig, C. Ischikawa and others have 

 done in other animals. I shall designate these zones as 1) the Forma- 

 tive zone, 2) the Growing zone, 3) the Ripening zone and 4) the zone 

 of Metamorphosis. 



I. The Formative zone. In the first part of this zone , the germ 

 cells (»Ursamenzellen«) are somewhat conical in shape and are con- 

 nected with the protoplasm of the supporting cell. The nucleoli of 

 the germ cells usually consist in their resting stage of two, three or 

 more granules. As in the »segmented skeina of Fie mming, the chro- 

 mosomes split longitudinally before the formation of the spindle figure 

 and the division of the niicleus takes place in the ordinary manner. 

 In this stage, we are not able to make out the exact number of chro- 

 mosomes in consequence of the small size of the cells, but it seems to 

 be 26 — 28. The same mode of division takes place two or three times 

 in this zone and the germ cells become two-thirds or less of their ori- 

 ginal size. 



II. The Growing zone. This zone is very conspicuous in the 

 testicular follicles owing to the groups of large cells contained in it. 

 The nuclear elements of these cells have the usual arrangement in 

 their resting stage. "When about to divide, the chromosomes become 



