14 UNIVERSITY OF MISSOURI STUDIES [202 



which the crayfish of Fig 6 has just discarded. The right chela, 

 left in the figure, had been broken ofif and had formed the new 

 growth indicated in the figure at a. When the moult took place 

 and the new chela was released from its confining shell, the ap- 

 pendage expanded to the size and proportions shown at a, Fig. 

 6. At the same time it might be well to call attention to some 

 of the other appendages that had been broken off. The first 

 right ambulatory appendage (Fig. 5, Z?) had been broken off be- 

 tween the ischiopodite and the meros. The injury had taken 

 place only a short time before, and, therefore, practically no new 

 growth had appeared, as is shown at h, in Fig. 6. Fig. 5 shows 

 a new growth (r), which had not yet been constricted into seg- 

 ments ; but that segments had been formed inside the integument 

 is seen by reference to Fig 6 (c). There the regenerated ap- 

 pendage shows the complete number of segments fully formed 

 and perfectly normal except in size. The left leg of the same 

 pair has made a no less remarkable growth; compare c (Fig. 5) 

 and c (Fig. 6). The left chela was broken off during the moult. 

 A comparison of Figs. 7 and 8, PI. II, also shows very clearly 

 that a considerable new growth is confined within the cuticle. 

 Both chelae (Fig. 7) have been regenerated and show that the 

 new growth (a) is of sufficiently long standing for the con- 

 strictions of the new segments to have been definitely formed. 

 The first pair of legs have also been regenerated and four of the 

 five new segments are apparent externally. In the moulted ap- 

 pendage, however, all five segments are present, h (Fig. 8). 

 Practically the same state of affairs may be seen from a com- 

 parison of c, d, and f (Fig. 7), and c, d, and / (Fig. 8), except 

 that in c (Fig, 8) the terminal segment of the new appendage 

 seems to have been broken off at the last moult. 



As has been previously mentioned, the length of time which 

 elapses between the loss of an appendage and the appearance of 

 a new one varies greatly in different individuals, and is depend- 



