686 



that this individual had been in the first-form condition before exu- 

 viation. The third animal — a moderately large second-form C. 

 virilis was taken while still soft from movilting September 4, 1900. 

 Since it had assumed the second-form condition just at the period 

 when all others were becoming first-form, it seems not at all impro- 

 bable that it would also represent one of those which retain the same 

 form after exuviation as before. With the possible exception of the 

 last, these specimens were all unquestionably old enough to show the 

 regular alternation of forms. 



Faxon, in his paper on Dimorphism, says: ,,I will add that the 

 males of extraordinary size which I have seen are all of the first-form. 

 Do these very old individuals cease to moult? Do they become per- 

 manently capable of reproduction?" While the most of the very large 

 males I have seen have been first-form I have seen some very large 

 second-forms and so must very much question the correctness of such 

 a theory. I may add, however, that it seems to me decidedly more 

 probable that the very old individuals should exuviate but remain 

 continually in the first-form condition than that they should cease to 

 exuviate altogether. 



No dimorphism in the males has been observed in Asiactis, nor 

 has any indication of it been found in any other genus of the Asta- 

 cidae, unless it be in the subgenus Camharoides where Faxon ^ suspects 

 the presence of two forms of the male as in Camharus. Should this be 

 found to be true, it would certainly be of great interest from a phylo- 

 genetic point of view. 



A fact Avhich has not heretofore been considered seems to me sig- 

 nificant. In Astacus, according to Chautrau^ after the third year the 

 males moult twice, first in June and July, afterwards in August and 

 September, and the females once, from August to September annually. 

 According to Huxley i", copulation takes place immediately after the 

 completion of ecdysisin the early autumn. It is to be observed 

 that if the alternation of forms in Cambai-us noticed by Faxon, occurs 

 regularly year after year, which my observations tend to show for both 



8 Faxon, Monograph, p. 227. 



9 Chautrau, S., 1) Observations sur la formation des pierres chez les écré- 

 visses. Compt. Rend. T. 78. p. 665—667. 2) Sur le mechanisme de la dissolution 

 intrastomacale des concrétions gastriques des écrévisses. Compt. Rend. T. 79. 

 p. 1230—1231. Also (3 and 4) Observations sur l'histoire naturelle des écrévisses. 

 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. Washing- 

 ton, 1896, and Huxley, F. H., The Crayfish. 



10 Huxley, loc. cit. 



