THE GERM-CELLS OF CICADA (TIBICEN) SEPTEMDECIM. 407 



great number of ovarian tubules containing a great many oocytes. 

 The oldest oocyte of a second stage pupa is about one seventieth 

 the linear size of the oldest oocyte of the adult, which shows 

 the tremendous growth that takes place in a few weeks. It has 

 been estimated (Marlatt, 1898) that the female Cicada lays 

 between 400 and 600 eggs. 



The male and female gonads were dissected out in Ringer's 

 solution and fixed in either Flemming's (strong), Bouin's, 

 Benda's, or Regaud's fixing fluids. Mitochondria were well 

 preserved by the Flemming, Benda and Regaud fluids, but were 

 either partially or wholly destroyed in Bouin's fluid depending 

 on the length of time the gonads remained in the fixing fluid. 

 Material fixed in Flemming's fluid (10 to 12 hours) was usually 

 the best for studying both chromosomes and mitochondria. 

 Sections were cut 8 to 10 micra in thickness and the stains used 

 were iron-haematoxylin (with and without counterstain), Benda's 

 crystal-violet and alizarin, and Altmann's fuchsin-methylene 

 green. 



The developing eggs were also collected from time to time for 

 a study of the chromosomes of the embryonic cells. These were 

 fixed in either Bouin's or Carnoy's fluids and were imbedded by 

 the celloidin-paraffine method. 



C. OBSERVATIONS. 

 i . Diploid Chromosome Groups. 



(a) Spermatogonia. The spermatogonia are found in the 

 proximal end of the ellipsoidal follicles of the testes. They form 

 a cap of cells at this end of the follicle containing the primary 

 and secondary spermatogonia. From the proximal end of the 

 follicle there proceeds a short narrow filament which contains 

 the spermatogonia of the multiplication stages. Mitotic figures 

 are quite abundant among the spermatogonia of the multiplica- 

 tion stages, but the metaphase plates are usually so crowded 

 that it is impossible to make accurate counts of the chromosomes. 

 On the other hand, the primary and secondary spermatogonia 

 rarely show cell divisions, but the metaphase plates when they 

 appear are very clear. 



The male chromosome number is 19, which indicates that there 



