HARRIS : DIMORPHISM OF CAMBARUS. 53 



Doctor Faxon suggests'' that Doctor Hagen's method of designat- 

 ing the two phases is not so happy as might be desired. 



It would, perhaps, be better if the terms were just reversed, and the 

 male in the condition to approach the female were called form II, 

 since that designated by Hagen as form II is the form in which we first 

 find the animal. While it is not at all descriptive, I can see, other than 

 that mentioned above, no serious objection to Hagen's terminology, 

 especially since it is so well established in the literature. It surely is 

 very convenient, while I am not at all sure that a descriptive term 

 which would not be cumbersome could be easily found. 



No dimorphism in the males has been observed in Astacus, nor, so 

 far as I have been able to learn, has any indication of it been found 

 in any other genus of the Astacidse, unless it be in the subgenus 

 Camharoids, where Faxon ^"^ suspects the presence of two forms of the 

 male, as in Camharus. Should this be found to be true, it would cer- 

 tainly be of great interest from a phylogenetic point of view. It 

 must be borne in mind, however, that the Parastacine genera have not 

 been nearly so thoroughly studied as those of the Potamobine. 



A fact which I believe has not heretofore been considered in the 

 literature on the dimorphism of Camharus nevertheless seems to me 

 significant. In Astacus, according to Chantran,^^ after the third year 

 the males molt twice, first in June and July, afterwards in August 

 and September, and the females once, from August to September, an- 

 nually. According to Huxley,^- copulation takes place immediately 

 after the comjyJetion of ecdysis, in the early autumn. It is to be ob- 

 served that if the alternation of forms in Camharus noticed by Faxon 

 occurs regularly year after year, which my observations tend to prove 

 for both C. immtinis and C. vir/lis, the parallel between the two is 

 quite striking ; the spring ecdysis of Astacus corresponding to that 

 which brings Camharus into the second-form after copulation, while 

 the autumn ecdysis of Astacus corresponds to that which brings Cam- 

 harus back into the form in which it is ready to approach the female. 



Neither Hagen's nor Faxon's material was in condition, having 

 lain so long in alcohol, for a microscopic determination of the condi- 

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

 to supply observations on this point, hoping, by careful comparison 



9. Faxon, "On so-called Dimorphism," etc. 



10. Faxon, Monograph, p. 227. 



11- Chantran, S. (1) "Observations sur la formation des pierres chez les 

 ('•crevisses," Compt. Rend., t. 78, pp. 665-667. (2) "Surle mechanisme de la 

 dissolution intra-stomacale des concr^^tions gastriques des (^crevisees," Compt. 

 Rend., t. 79, pp. 1230, 1231. (3, 4) "Observations sur 1' hietoire naturelle 

 Ecra^sses," Compt. Rend., t. 69 and 73. 



I have not seen these papers, but make the statement on the authority of Dr. C. L. Herrick, 

 "The American Lobster," Bull. U. S. Fish Com., vol. XV (Washington, 1896), and Huxley (T. 

 H.), "The Crayfish." — j. a. h. 



12, Huxley, loc. cit. 



