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NATHAN FASTEN 



Text figure A shows a dorsal view of the testis during the month 

 of July, the period when the most active proliferation occurs 

 on the part of the cells. From this drawing, as well as that of 

 Miss Steele in her paper on the crayfish of Missouri ('02) it is 

 evident that the testis of Cambarus virilis differs considerably 

 in shape from the testis of Astacus fluviatilis as pictured by 

 Huxley. Structurally they are very similar, being made up of a 

 great number of vesicles or tubules called acini, which are con- 

 nected by short branches of the ultimate ramificalrions of the 



V. d. 



Text figure A Dorsal view of testis of Cambarus virilis; a. L, anterior lobes; 

 ?n.l., median lobe; v.d., vas deferens. 



vas deferens. The testicular lobes thus present the appearance 

 of bunches of grapes, the grapes representing the tubules or 

 acini, and the stalks, the branching ramifications of the vas 

 deferens. 



2. Variations in the testis throughout the year 



The testis of Cambarus virilis was studied monthly and con- 

 siderable variation was found to exist in its size as well as in the 

 state of the germ cells. During April and May the testis is 

 comparatively small and most of the tubules are either empty 

 or filled with mature spermatozoa, early spermatogonial stages, 

 nurse cells, or germinal epithelium cells. In June, the testis 



