INSECT SPERMATOGENESIS 625 



EXPLANATION OF PLATES 24-26. 



All of the figures have been outlined as far as possible with 

 the camera lucida at an initial enlargement of approximately 

 3,800 diameters. At so great an enlargement it has of course 

 been necessary to correct the outhnes extensively and to add 

 much of the liner detail free hand. In reproducing, the figures 

 have been reduced uniformly, those of Pis. 24 and 25 to an 

 enlargement of approximately 2,530 diameters, those of PI. 26 

 to approximately 3,000 diameters. All of the figures are from 

 material fixed in Flemming without acetic acid, except figs. 42, 

 43, and 44, which are from material fixed in Champy. 



Reference Letters. 



A, acrosome. B, nuclear body of doubtful nature. C, centriole(s). 



/, tail filament, (t, Golgi apparatus = acroblasts (where the acroblasts are 



much scattered, only a few representative ones are specifically labelled). 



K, nucleus. M, mitochondria. N, nebenkern. S, central substance. 



V, vesicles developed on the mitochondrial tail sheaths. 



Plate 24. 



Explanation of Figures. 



All the figures are from Pygaera bucephala. Figs. 1, 

 2, and 3 are from the same cyst of developing sperms ; likewise 

 tigs. 4 and 5, and figs. 8 and 9 ; figs. 10, 11, and 12 are from 

 a cyst of abnormally large spermatids. 



Figs. 1, 4, 8, 10, and 13. — Progressive stages in the elongation of the 

 nebenkern. The acrosomal granule is stained i^jtensely black. 



Fig. 2. — Section through a spermatid nucleus, showing the acrosomal 

 granule in two parts, and numerous Golgi bodies, some of which seem to 

 be engaged in depositing their quota of acrosomal material. 



Figs. .3, 5, and 6. — Cross-sections through the nebenkern in successive 

 stages of its elongation to show the structure of the chromophilic material. 



Fig. 7. — Portion of the distal end of the nebenkern showing the con- 

 striction of the chromophobic material to form the tail vesicles. 



Fig. 9. — Cross-sections of the nebenkern at the stage of fig. 8 : A and B, 

 through the region of the chromophilic material ; C, through the chromo- 

 phobic material above the plane of A and B. 



Fig, 11. — Frequent appearance of tail vesicles when fully formed. 



