On the Spermatogenesis of the Silk-Worm- (r) 



BY 



Kametaro Toyama, Assistant in the Zoological Institute, 

 Agricultural College. 



With Plates III— IV. 



The work which forms the subject of the following pages 

 was carried on in the Zoological Institute of the Agricultural 

 College during last year. My original intention was to determine 

 the question, whether Verson's large cell in the blind end of the 

 testicular follicle is truly a genital cell or not, and in studying 

 this I also touched upon the entire developmental history of 

 the spermatozoa as well as the most interesting question in the 

 development of genital cells, namely: the reduction of the 

 chromosomes. 



Before going any further, I have, in the first place, to 

 express my sincere gratitude to Prof. Ishikawa for his kind 

 guidance and friendly counsel throughout the progress of my 

 work in his laboratory. I am also very much indebted to Prof. 

 Mitsukuri of the Science College for his kindness in allowing me 

 to use the library of the Science College, and also for various 

 other matters. To Prof. Sasaki I am also much indebted for the 

 materials. Thanks are also due to the director of the College, 

 Prof. Matsui who allowed me to continue my work in the College 

 after I passed through the university courses. 



Methods of Investigation. The entire process of the spermato- 

 genesis was studied by means of sections and teased preparations, 

 the former method affording more advantages than the latter for 

 the researches of the division of the genital elements. 



For teasing the testicular follicles, I used acetic acid 

 methylgreen for fixing and staining. As this causes the swell- 

 ing of the chromosomes, it is very useful in calculating their 

 number. 



The following fluids are used in hardening the sections : 

 picro-acetic acid, sublimate alcohol, salt sublimate, chromo- 



(i) The preliminary note of this paper was published in the " Zoologischen 

 Anzeiger " No. 438 this year. 



