REVIEWS OF RECENT LITERATURE. 
PSYCHOLOGY. 
Individual Psychophysiology of the Crayfish. — In what sense, 
if at all, may the term “individuality” be applied to the crayfish? 
is the question which Dr. Dearborn! has attempted to answer experi- 
mentally. - 
Starting with the definition, *a living organism is an individual in 
proportion to the relative constancy and strength of its own proper 
tendencies considered as manifestations of an inherent will" the 
writer, by studying the individual reactions of about twenty repre- 
sentatives of Cambarus affinis, arrives at the conclusion that there is 
no evidence of psychic individuality. 
The experiments upon which this conclusion rests are: 1. The 
determination of traction strength, or the pulling power of the ani- 
mal. The traction power per gram of body weight varies from 1.7 
to 3.5. Three tests were made for each individual on different days, 
and great variation is noticeable. 2. The pinching power of the 
chele, 3. Returning habits ; the crayfish being placed on its back 
on a glass plate and allowed to right itself if possible. In this, too, 
there is remarkable variability. It is an interesting and suggestive 
experiment, by the future use of which much should be learned con- 
cerning the mechanism of the crayfish. 4. Training in the returning 
habit. Training was given in a particular method of returning, but 
with negative results. 5. Reactions to galvanism. 6. Galvanotro- 
pism. The animals invariably go to the cathode, although at widely 
differing rates. 7. Hypnosis. Crayfish are easily hypnotized by 
holding them firmly in a stable position for a short time. Dr. Dear- 
born emphasizes the fact that the time necessary for hypnosis varies 
greatly in different animals and in the same animal from time to 
time, as does also the duration of the hypnotic influence. He differs 
from Verworn in holding the process of hypnosis in the crayfish to 
be the same as human hypnosis. 8. Reaction time. The reaction 
of the forceps of the chele to tapping on some part of the shell (the 
! Dearborn, G. V. N. Notes on the Individual Psychophysiology of the Cray- 
fish, Amer. Journ. of Physiol., vol. iii, No. 9 (1900), pp- 404—433 
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