SUTTON: SPERMATOGOXIAL DIVISIONS IN BRACHYSTOLA MAGNA. 157 



1885. Voigt. Ueber Ei- unci Samen-bildung bei Branchiobdella. Arh. 

 Wticrzhnru. Bd. VII. 



189(5. Wagner, J. Beitrage zur Kenntniss der Spermatogenese bei den Spin- 

 neu. Arh. X(tt. rVr.v. ,S7. Pcfrrshio-f/. Vol. XXVI. 



1895. Wilcox, E. V. Spermatogeneses of Caloptenus femur-rubrum and Ci- 

 cada tibicen. liitll. Mils. Cniiij). Ziiol. Vol. XXVII. 



EXPLANATION OF PLATES XXXII, XXXIII, XXXIV, XXXV. 



All drawings are from camera lucicla outlines. For all except fig. 1, a 

 B. & L. i^j-inch oil immersion objective and a 1-inch B. & L. ocular 

 were used. The length of the tube for all drawings was 160 mm., and 

 the drawing-board was at the height of the stage. For fig. 1, a B. & L. 

 ,V-inch objective was used, the other conditions being those named 

 above. In reproduction, the drawings are reduced one-fourth, giving 

 a final magnification of 1375 diameters for fig. 1, and 900 for the others. 



Figs. 2 to )58, inclusive, are numbered as nearly as possible in 

 the order of their development, with the exception that fig. 3*> properly 

 belongs between figs. 19 and 20. 



The photomicrographs were made with a Zeiss 2-mm. apochromat 

 objective and a Zeiss projection eyepiece. The source of illumination 

 was the crater of the electric arc. 



Figs. G and D have an actual magnification of 728 diameters, 

 and the remaining figures 1120 diameters, being reduced one-fifth in 

 reproduction, from 910 and 1400, respectively. 



Drawings and photomicrographs are by the author, the latter 

 especially, with valuable assistance from Professor McClung, 



1)RAWIN(;S. 



Fig. 1. Longisection of blind end of follicle, showing all of spermatogonia and 

 one cyst (A'y>(^-) of spermatocytes. The cyst membranes may be plainly seen 

 around their respective spermatocysts; and between the latter, the primary 

 spermatogonia with their large, vesicular nuclei. Many of the secondary 

 spermatogonia show the vesicular condition of the accessory chromosome, 

 while the prominent black objects on peripheries of the spermatocyte nuclei 

 represent a later stage of the same. At n, n, may be seen the nuclei of the 

 follicular wall. 



Fig. 2. Resting stage of primary spermatogonium, chromatin arranged in patches 

 connected by linin threads. Quantity of cytoplasm is unusually large. 



Fig. 3. Early stage of development of primary spermatogonium — chromatin 

 becoming more diffused. 



Fig. i. Slightly later stage. Chromatin almost ready for the formation of the 

 spireme. 



Fig. 5. Early prophase. A number of spiremes enclosed in a single nuclear 

 membrane. 



Fig. G. Later prophase. Spiremes short and thick and connected by linin fibers. 



k 



