HARRIS : CRAYFISHES GENUS CAMBARUS. 65 



condition, as in the first-form. In a letter of October 29, 1901, 

 Prof. W. P. Hay, of Washington, whose work on the crayfishes 

 is well known, and whom I have to thank for various courte- 

 sies, says : "I think you are entirely correct in your observa- 

 tions, and have settled some points beyond doubt. I have 

 long been of the opinion that males of the second-form are not 

 sterile, for I have often seen them copulating, and, after the act 

 was completed, have found masses of sperm on the sternites of 

 the female. Of course, the spermatozoa might be inert, but 

 such a condition would, so far as I know, be without parallel." 

 This observation of Professor Hay's I regard as important, 

 considering the highly different physical characteristics of the 

 two forms, their constant occurrence in all the well-known 

 species of the genus, and the absence, so far as we now know, 

 of such in the other genera of this family, unless it be in 

 Cambaroides. 



THE CONJUGATION OF CAMBARUS. 



Mr. E. A. Andrews first published observations on this sub- 

 ject. In the American Naturalist he ('95) describes the proc- 

 ess in detail, giving two figures from photographs. In the 

 Zoologischer Anzeiger he gives (956) about the same observa- 

 tions in condensed form. The following is quoted from his 

 paper in the Zoologischer Anzeiger : 



"Some observations on the breeding habits of Cambarus af- 

 finis show that there are imj)ortant differences between the 

 American crayfish, Cambarus, and the European crayfish, Asta- 

 cus, and that certain structures hitherto known only as specific 

 and generic characters are necessary accessory reproductive 

 organs. 



"1. When kept in confinement Cambarus o^ms conjugated 

 in November and in February, March, and April. 



"2. The process lasts several hours. 



"3. The male exhibits great skilland persistency, and isvisibly 

 excited throughout the process, while the female is from the 

 first passive and inert and shows scarcely any evidence of ex- 

 citement. 



"4. The sperm is introduced into the cavity in the annulus, 

 which thus serves as a sperm receptacle, as in the lobster, 



2-Bull., No. 3, 



