570 Charles Zeleny 
6 The Chele of Cambarus bartoni. (Tables 18 to 21)" 
The crayfish used in these comparisons were all reared in the 
laboratory from one mass of eggs. Fifty individuals were obtained 
in this way. 
Two comparisons are made, one between individuals with a 
single chela removed and the other between individuals in which 
both chela were removed. The comparison in each case is 
made between individuals operated upon one day after the fourth 
molt and others operated upon after the eighth, ninth or tenth 
molt. In each case the actual length of proliferated material is 
greater in the older individuals but the specific rate is less in 
the older than in the younger ones. The specific amounts of 
regeneration are nearly the same in the crayfish of all ages with 
a single chela removed and greater in the younger than in the 
older ones in the individuals with both chelz removed. 
The data as a whole favor the view that the actual rate of 
proliferation is greater in the older than in the younger individuals 
but not great enough to enable them to complete the lost part 
as soon as in the younger ones. 
7 Palemon tenuicorns. (Table 22)” 
The data are obtained from a set of twenty-one individuals 
operated upon in June, 1906, at Tortugas. A comparison is made 
of the rate of regeneration of a single removed chela during one 
molt. Six individuals were taken during their third regeneration 
of a chela and three during their second regeneration. In each 
case the length of the regenerated chela increases with increase 
in size (age ?) of the animal. ‘The specific rate, however, decreases. 
For the specific. amount of regeneration during the single molt 
no definite conclusion can be reached. 
The data here as in the case of Cambarus bartoni show an 
increase in the rate of proliferation of material between the sizes 
of 6.8 and 13.1 mm. but this increase is not sufficient to enable 
4 Based wholly on new data. 
2 Based wholly on unpublished data. 
