502, Charles Zeleny 
6. The Chelz of the Wood’s Hole Shrimp, Palazmonetes 
vulgaris, Stimp. 
Method. In the case of the Wood’s Hole shrimp the object of 
the experiment was the comparison of the rate of the first regenera- 
tion of the right chela with the simultaneous second regeneration 
of the left chela and vice versa. ‘The advantage of this method 
consists in the elimination of differences between individuals. 
The principal source of error is the possibility of inherent physio- 
logical differences between the two chele. ‘This error is in all 
probability negligible because there 1s little evidence of a structural 
difference between the two chelz though the rightis on the average 
slightly larger than the left. Since the left chela was removed in 
twenty-five individuals, and the right in twenty, constant latera. 
differences are practically balanced. ‘The only error is that of 
possible individual lateral differences and this is eliminated by the 
large number of shrimps used. 
A peculiarity of this method as compared with the others, 
except Cassiopea, should be emphasized. ‘The result cannot be 
directly compared with the results of the prev-ous series on the 
crayfish. If the effect of the removal of a chela as far as rate of 
future regeneration is concerned is a purely local matter in olving 
merely the immediate neighborhood of the wound the comparison 
is valid. If, however, as we have many reasons for- believing, the 
effect of the operation involves the general physiological condition 
of the animal as a whole the first removal and regeneration of a 
chela may have as much influence upon the future regeneration 
of the opposite one as upon its own second regeneration. If this be 
true we may expect the two rates to be equal whether the general 
effect of successive removal be positive, negative or indifferent. 
Fifty-one shrimps of approximately equal size were selected 
from the smaller individuals of a lot of about three hundred col- 
lected on August 15, 1906, at Wood’s Hole, Mass.?° Forty-five of 
these were used in the present experiment and thirty-one are valid 
70] am indebted to Mr. Sergius Morgulis for kindly consenting to take care of the shrimps 
after my departure from Wood’s Hole. Without his help I should not have been able to 
complete the experiment. 
