23 l] REGENERATION OF CRAYFISH APPENDAGES 33 



Structures were in two individuals (C. virilis) of medium size 

 from which the entire right eye had been removed on March 15. 

 One of them moulted April 9, the other April 15. At the time 

 of this moult neither of the crayfish showed any indication of a 

 new structure. The individual that moulted April 15, under- 

 went a second moult on May 24, and at this time a well-devel- 

 oped antenna-like structure made its appearance. The crayfish 

 also that moulted April 9 moulted a second time on May 25, and 

 again the same kind of segmented structure appeared. In each 

 case the appendage consisted of a pair of flagella, each of which 

 was composed of a number of segments. The flagella did not pro- 

 ject directly outward but curved slightly forward. The inner or 

 anterior flagellum was smaller and shorter than the outer, pos- 

 terior one. The flagella on the first individual were longer and 

 slenderer than those upon the other one. Unfortunately, how- 

 ever, I lost the specimen before a drawing had been made of 

 this interesting structure. Fig. 27, PI. IV, shows the shorter, 

 blunter antenna-like product of regeneration in the second cray- 

 fish, together with the eye on the opposite side. There is no 

 enlarged segmented base, as in the normal antenna or antennule, 

 but only a slightly enlarged and rounded elevation from which 

 the flagella arise. No conspicuous setae are developed upon 

 them. 



After obtaining these two specimens a number of other 

 crayfish were operated upon without any definite results, the 

 trouble being that most of them died before a moult occurred. 

 It may be said, however, that a majority of those that died with- 

 out moulting were from among the number that were operated 

 upon in the fall and were kept in the laboratory all winter. 



Type II : A single flagelhun regenerated. Besides the two 



crayfish discussed under Type I, I have obtained but two or 



three specimens that showed similar structures; and in these 

 3 



