568 Charles Zeleny 
EXPERIMENTS ON ANIMALS WITH A MOLTING HABIT 
4 The Chele of the Guljf-weed Crab, Portunus say: 
The age factor is discussed in detail in the original paper in 
which Tables 10, 11A and 12 refer especially to it. The general 
result only need be mentioned here. In 66 crabs ranging in 
cephalo-thoracic length from 3.9 to 14.5 mms. not only the rate 
of formation of new material but also the specific rate or rate 
per unit of cephalo-thoracic length increases with increase in 
size of the crab. ‘The increase in specific rate is however asso- 
ciated with a corresponding increase in length of the normal 
uninjured chelz in larger individuals. Perfectly normal chelze 
should therefore be obtained as quickly in large (old ?) individuals 
as in small (young ?) ones between the sizes mentioned. 
5 The Chele of Cambarus propinquus. (Tables 12 to 17)° 
The data are taken from two series of young crayfish reared 
in the laboratory, one with 70 and the other with 93 individuals 
and one series of old crayfish with 74 individuals. 
Two comparisons are made. ‘The young individuals (Tables 
12 and 13) are compared with adults (Tables 14.to 17) and 
among the adults the smaller individuals are compared with the 
larger ones*(Yables 14,\15, 160cand 17): 
Taking first the comparison between young animals and adults 
it is found that crayfish operated upon two days after the fourth 
molt have regenerated on the average 2.12 mm. of the propodite 
of the removed chela’ in 14.6 days in two molts. The specific 
amount is 0.326 and the specific rate 0.0229. Tnose operated 
upon one day after the fourth molt have regenerated 1.86 mm. 
8 The full data are published in the paper on ‘‘Regeneration in the Gulf-Weed Crab, Portunus 
sayi.”” Carnegie Institution Publications. Tortugas Laboratory Reports, vol. 2. 
* Based partly on new data and partly on data from the paper on “The effect of the degree of injury 
upon the rate of regeneration.” Journ. Exp. Zodl., vol. ii, 1905. 
10 Throughout the paper in speaking of the ‘length of the chela” the greatest length of the propo- 
dite is meant. 
