ON THE SPERMATOGENESIS OF THE SILK-WORM. I27 



and the left side of the dorsal vessel over the alimentary 

 canal, in the segment where the sixth stigmata opens (namely 

 eighth segment) and are firmly attached to the body-wall by 

 the trachea of the sixth stigmata and fatty tissues. As in 

 other Lepidoptera, each testis consists of four blind tubes or 

 testicular follicles, which are covered with a common envelope, 

 tunica adventitia, and each is placed facing the other with 

 the concave side, on both sides of the dorsal vessel. From 

 the middle of the concave side of each of these testes one 

 vas deferens arises, and the testicular follicles enter into it. 

 These ducts run, at first, along the dorsal side of the body, 

 gradually changing their course into the ventral side, and 

 finally attach themselves with a uterus-shaped process (fig 3) 

 found on the ventral median side of the twelfth segment. This 

 process seems to be changed into seminal vesicle, accessory 

 glands and ductus ejaculatoris. 



In the female organs, all the relations are nearly similar 

 to that of the male except the shape of the ovary and the 

 mode of the attachment of the oviducts with it. The ovary 

 of the silk-worm is smaller than the testis from the early 

 beginning till to the last of the larval stage. It is somewhat 

 triangular in shape, and is situated each side facing the other 

 with a side of a triangle, the angles opposite to these sides 

 being produced to form the oviducts. 



This is the usual form of the genital organ of Bombyx 

 mori in its larval stage (Fig. 1 — 2). Cases are, however, 

 met with where the vas deferens arises from the outer side 

 of the testes as in the ovary, or one of the testes with its 

 vas deferens on its inner side and the other on the outer side. 



Terminology. The question of nomenclature presents some 

 difficulty, since so many different names have been given to 

 the same elements by different observers. So far as I could, 

 I have tried to avoid the use of such general terms as "sper- 

 matoblast," "spermatocyte," "spermatogone," etc. and have 

 substituted simple descriptive expressions, as has been done by 

 O. Hertwig, C. Ishikawa, and vom Rath. We may distinguish 

 four stages in the sperm-formation of Bombyx mori. The 

 first of which, we may call the formative stage (" Keimzone " of 

 German authors), the second the growing stage (" Waschsthums- 



