SPERMATOGENESIS IN PARATETTIX. 269 



high, rather short, protoplasmic keel. No keel has been observed 

 as forming a part of the middle piece of P. leuconotiis-leucothorax. 

 The head is many times thicker then the tail and is decidedly 

 arrow shaped. The middle piece seems to continue from the 

 head to the long filamentous tail without a definite dividing line 

 between them. 



SUMMARY. 



1. Paratettix huconotus-leucothorax has thirteen spermatogo- 

 nial rod-shaped chromosomes, four larger and nine smaller ones. 



2. Neither the larger nor the smaller chromosomes form equal 

 sized pairs. 



3. The four larger chromosomes and one of the smaller ones 

 are bent rods, the others are almost straight. 



4. Neither spermatogonial chromosome has been surely 

 identified as the accessory chromosome. 



5. In the growth period is a mass of chromatin which is more 

 compact and stains more intensely than the remainder of the 

 chromatin. This is the accessory chromosome of the first 

 spermatocyte. 



6. The first spermatocyte chromosomes are formed in vesicles. 



7. There are six dumb-bell-shaped bivalent chromosomes 

 and one ovoid univalent chromosome in the primary spermato- 

 cyte. 



8. The accessory is near the periphery of the nucleus and 

 passes to one pole undivided slightly in advance of the other 

 chromosomes in the first spermatocyte division. 



9. The bivalent chromosomes divide crosswise. 



10. The accessory chromosome divides in the second division. 



11. The spermatozoon has an arrow-shaped head and a long 

 filamentous tail. 



BIBLIOGRAPHY. 

 Artom, C. 



'09 Cromosomi ed eterocromosomi nelli cinesi spermatogenetiche di Stauronotus- 



maroccanus Thumb. Biologica, Vol. 2. 

 Buchner, P. 



'09 Das accessorische Chromosom in Spermatogenese und Oogenese der Or- 

 thopteren, Zugleich ein Beitrag zur Kenntnis der Reduktion. Archiv fur 

 Zellforschung, Bd. 3, Hft. 3. 

 Brunelli, Gustavo. 



'10 La Spermatogenesi della Tryxalis. Division! Spermatogoniali. Memorie 

 della Societa Italiana Scienze, Tome 16, serie 30. 



