34 UNIVERSITY OF MISSOURI STUDIES [222 



instances a single flagelltim and not a pair of flagella was devel- 

 oped. These crayfish were smaller than those mentioned under 

 Type I and all belonged to C. gracilis instead of C. virilis. The 

 regenerated structure of Type II is represented in Fig. 33, PI. 

 IV. The crayfish from which this figure was obtained had the 

 entire left eye removed on April 21, shortly after the animal was 

 brought into the laboratory. On June 19 it moulted and at that 

 time there appeared a segmented structure similar to an ordinary 

 flagellum. The flagellum consisted of fourteen segments spring- 

 ing from a slightly elevated base. Before the moult occurred 

 the structure was coiled back upon itself just as in the regener- 

 ating flagellum of an antenna. Even after the moult, it did not 

 uncoil immediately. Fig. 33 shows the flagellum after un- 

 coiling and in its relation to the antenna and antennule. The 

 flagellum from the eye-stump curves upward towards the ros- 

 trum and is longer than the rostrum ; compared with the flagel- 

 lum of the antennule it is shorter and thicker. The other appen- 

 dages of this type) showed no features not seen in this, except 

 that in one case, at least, the regenerated flagellum did not pos- 

 sess as many segments as are represented in Fig. 33. A shorter 

 time, however, had elapsed between the removal of the eye and 

 the occurrence of the moult. 



Type III : Segmented horn-like structures. A number of 

 crayfish from which the entire eye had been removed showed, 

 after moulting, not an antenna-like structure, as in the previous 

 cases, but a short horn-like growth which consisted of two, three, 

 or even as many as five or six segments. Types of this structure 

 are shown in Figs. 31, ^2, 34, PI. IV. Fig. 3 (n) shows a regen- 

 erated appendage consisting of but two segments besides the 

 rounded base ; the distal segment is relatively very much smaller 

 than the proximal one. The segments are not movably articu- 

 lated and the whole structure is covered with a dense hard cut- 



