294 PROCEEDINGS OF THE ACADEMY OF [April, 



SPERMATOGENESIS IN LEPIDOPTERA. 

 MARGARET HARRIS COOK, PH.D 



Contents. 



PAGE 



Introduction 294 



I. Previous Work 295 



II. Material and Methods 29S 



III. Ohservations 299 



A. Callosamia piomethea 301 



1. Spermatogonia 301 



2. Growth Period of the Spermatocyte 302 



3. Prophase of first Maturation 303 



4. Maturation Divisions 305 



5. The Idiochromosomes 305 



6. Metamorphosis of the Spermatids 306 



7. Centrosomes 307 



B. Telea polyphenols 309 



C. Antomeris io 311 



D. Samia ceeropia 312 



E. Acronycta sp 314 



F. Spermatids and Spermatozoa 315 



IV. Theoretical Considerations 317 



V. Summary 320 



VI. Literature 322 



Description of Plates I-VI 324 



Introduction. 



Ever since Henking's work on the spermatogenesis of Pyrrhocoris 

 apterus (1891) it has been known that in one maturation division one 

 chromosome may go undivided into one of the daughter cells, so giving 

 two classes of spermatids. The significance of this fact was not recog- 

 nized until ten years later, when McClung (1901) advanced the purely 

 theoretical view that this dimorphism of the spermatozoa bore a direct 

 relation to the determination of sex, and suggested that the spermatozoa 

 containing the extra chromosome, which was called by him the acces- 

 sory chromosome, were the male determinants. In 1905 Stevens for 

 Coleoptera and Wilson for Hemiptera showed, by comparing the number 

 of chromosomes in the spermatocyte and oocyte, that the accessory 

 chromosome had its homologue in the egg and hence was the female and 

 not the male determinant. That this marked difference in the behavior 

 of the accessory chromosomes from the other chromosomes in one of 

 the maturation divisions, together with the new interpretation of its 



