32 Comparative Psychology. [January, 
Hence migration may be regarded as a complicated result 
of natural selection, heredity, and perceptive and conceptive 
impulse. It must also be remembered that birds often set 
out too early or too late, and consequently suffer; and that 
multitudes evidently fail to find their way back to their 
original home, as may be gathered from the want of increase 
in their numbers. 
An interesting fadt is cited to prove that birds are formally 
educated by their parents. Young crossbills are supplied 
at first with pine-cones which are fully opened, then with 
half-opened ones, and finally with such as are closed, and 
are thus gradually trained in the art of finding and picking 
out the seeds. 
The author's explanation of slave-holding among ants does 
not appear to us satisfactory. He refers this custom to mere 
perceptive impulse. The plunderers carry strange pupae 
into their nests from a mere perceptive impulse, just as a 
bird will steal the eggs of other birds to sit upon. That the 
ants thus born in a strange city remain there and work in 
their accustomed manner need not surprise us. 
We think that Dr. Schneider here overlooks the faCt that 
the slave-ants occupy a manifestly distinct and subordinate 
position, and when dead are treated with less ceremony than 
the free citizens. It would be very important to make fresh 
observations on slave-making ants from this point of view. 
The further question why any animal should like those 
things which are favourable to the preservation of the indi- 
vidual or the species, and should shun all that are hostile, 
scarcely needs answering. Suppose any creature had an es- 
pecial liking for poisonous food : it must necessarily perish, 
as multitudes no doubt have done, those only surviving 
whose taste were in better harmony with the conditions of 
existence. 
Dr. Schneider, whilst tracing many of the habits of 
animals to direCt unconscious perceptive impulses, does not 
fall into the common error of claiming thought as an 
attribute of man alone. He gives on good authority in- 
stances of complicated action on the part of several of the 
higher animals, involving formal, conscious contrivance and 
a calculation as to what a man or other animal would be 
likely to do under such circumstances. He considers, how- 
ever, that man only a( 5 ts on fixed principles. An entire 
number of the “Journal of Science” would not suffice for 
the most superficial discussion of half the interesting con- 
siderations here brought forward. But the only really 
appropriate criticism of the work must be conducted in the 
