ANATOMY OF STYLETS OF CAMBARUS AND ASTACUS. 9 1 



The second stylets of Astacus and of Cambarus have the value 

 of pleopods that have merely added a lateral outgrowth which 

 arises in larval life and serves as an accessory organ in sperm 

 transfer. 



It is evident that the stylets of the species of Cambarus studied 

 are much more highly specialized than the stylet of the American 

 Astacus studied and this in turn seems less generalized than the 

 Astacus of Europe. 



The stylets of Cambarus could be readily derived from those of 

 Astacus by specialization. The addition of glands, the strength- 

 ening of the shell, the refinement of the conducting tubule and 

 the perfection of the accessory stylet in Cambarus may all be 

 regarded as correlated with the presence of the annulus and 

 sperm pocket in the females in this genus : the more accurate 

 apparatus of the male Cambarus being used for a much more 

 specialized task. 



The first stylets in both genera might be derived from a flat 

 stylet similar to that in the lobster where, probably, the two, 

 right and left, are used at the same time to fill the sperm 

 receptacle. 



Upon this assumption we would regard Astacus as having lost 

 some sort of a sperm receptacle which has been retained and 

 perfected by Cambarus. 



REFERENCES. 



1. Andrews, £. A. 



'04 Breeding Habits of Crayfish. Am. Naturalist. 



2. Andrews, E. A. 



'06 The annulus ventralis. Proc. Boston See. Nat. Hist., 32. 



3. Hagen, H. A. 



'70 Monograph of the North American Astacidae. Mem. Mus. Com. Zool. 

 Harvard. 



4. Faxon, W. 



'85 A revision of the Astacidas. Mem. Mus. Com. Zool., 10. 



5. Soubeiran, L. 



'65 Sur I'Histoire naturelle et 1' Education des Ecrevisses. Compt. Rend. Acad. 

 Sci. Paris, vol. 60. 



6. Chantran. 



'70 Ibid., vol. 71. 



7. Huxley, T. H. 



'80 The Crayfish. New York. 



8. Whitman, C. 0. 



'9I Spermatophores as a Means of Hypodermic Impregnation. Journ. of Mor- 

 phol., vol. 4. 



