603 
book dealing with this subject has already appeared in Science, 
XIV. Aug. 1901. 
Regeneration ofthe Appendages of the Crayfish. 
I have made a few experiments on the crayfish similar to some 
of those on the hermit-crab. The conditions in the crayfish are some- 
what different in so far as a true breaking-joint exists only in the 
first pair of legs. The four walking legs of each side may also be 
cast off at the base if they are after injury, held firmly — the 
breaking taking place at a joint between two segments that corresponds 
in position to the breaking-joint on the first pair of legs. If the first 
pair of legs are cut off outside of the breaking-joint the stump is 
soon cast at the base, but if the other legs are cut off distal to the 
second basal joint the stump is very often retained — at least in the 
species that I have had. 
Small individuals (for the most part young animals) were used, 
They were kept during the winter in the laboratory in flat dishes con- 
taining just enough water to cover the crayfish. Once or twice a 
week the crayfishes were fed with worms. Some of the animals were 
kept for eight months. 
If the first leg of either side is cut off inside of the breaking- 
joint a new leg is regenerated. The same statement applies to the 
walking legs, so far as I have examined them. When the walking 
legs are cut off outside of the breaking-joint and are not subsequently 
cast off at the base, no regeneration takes place at the cut-end in 
15 16 Ic 
most cases, at least none that can be seen from the outside. In one 
case, however, represented in Fig. 15, a new distal end regenerated 
