687 



C. immuìiis and C. virilis, the parallel between the two is quite strik- 

 ing; the spring ecdysis of Astacus corresponding to that which brings 

 Cambarus into the second form after copulation, while the autumn ec- 

 dysis of Astacus corresponds to that which brings Cambarus back into 

 the form in which it is ready to approach the female. 



Neither Hag en's nor J axon's material was in condition, having 

 lain so long in Alcohol, for microscopic determination of the character 

 of the contents of the testis. My object in this study has been to 

 supply observations on this point, hoping, by a careful comparison of 

 the sexual organs, to get some idea of the relation of the reproductive 

 elements to the physical condition of the animal and so come a little 

 nearer to the determination of the true significance of the occurrence 

 of the two forms. My material was prepared by the usual cytological 

 methods; Flemming's fluid was used as a fixative and Heiden- 

 hain's Iron-Haematoxylin and the Safranin-Gentian, Violet-Orange, 

 and Combination were used principally as staining reagents. 



I have carefully examined sections of the testes of thirty seven 

 individuals taken at various times throughout the year. Some periods 

 are not represented, yet I feel sure that the material so far studied war- 

 rants me in drawing the conclusions given in this paper. I expect, 

 however, to complete my series of testes as soon as possible and shall 

 then publish the results obtained from a study of the condition of testes 

 throughout the year. In many cases all three lobes and the vas defe- 

 rens were examined; in others, sections were prepared from only one 

 or two of the lobes or the vas deferens. It is, of course, unnecessary 

 to state that in drawing comparisons between individuals, care was 

 taken to have the size and general physical condition of the specimens 

 as nearly the same as possible. 



Examination of material taken in late July and in August shows 

 about the following condition. At the proximal end of the testis are 

 a few emptied follicles. Back of this is a region of follicles containing 

 spermatids in various stages of transformation, the earlier stages being, 

 for the most part, toward the distal end. The spermatid region extends 

 usually somewhat more than one half the length of the lobe. Then 

 follow spermatocytes, of which two or more follicles are often seen to 

 be in active mitosis, and finally a zone of spermatogonia about one 

 sixth of the length of the lobe in width. An occasional spermatogonial 

 division figure is to be seen. The vas deferens is partially filled with 

 spermatozoa. 



The above is the condition found in both first- and second-forms 

 and a very careful examination of material from seventeen individuals 

 collected from July 27 to Aug. 31 did not reveal any differences which 



