eA Lier 
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LEAURSDAY, JUNE Mii ior. 
THE PURPOSE OF VOULH. 
The Childhood of Animals. By Dr. P. Chalmers 
Mitchell. Pp. xiv+269+plates. (London: 
W. Heinemann, 1912.) Price 10s. net. 
HIS remarkably fine book is a work of dis- 
tinction—both of style and insight. When 
an author has a story of his own to tell and knows 
how to write, the outcome is often a book of de- 
lightful descriptive natural history, but Dr. Chal- 
mers Mitchell has much more to give us than that. 
He has succeeded in making us read biology with- 
out knowing it. With a charming subject to start 
with, with a wide experience to draw from, with 
an infectious sympathy for youth, and with a well- 
thought-out biological system, he has given us a 
really big book—and happy are those who have 
found it. A great pleasure it is to discover:a 
work with so many interesting facts and so whole- 
some a salting with ideas, written in a style that 
is individual and charming. We congratulate 
the author on achieving a conspicuous success. 
Most naturalists like their natural history “dry,” 
and few of them have much use for popular ex- 
positions, but “The Childhood of Animals” is a 
book by itself, which takes a grip. The author 
has been extraordinarily fortunate in his artists; 
the Japanesque colour-studies are revelations of 
character and the black and white drawings are 
also very pleasing and effective. 
Without insisting on it too much, the author 
divides animals into three sets—those which have 
no youth, such as amoebe (but is it not rather 
that they never grow up?); those which are quite 
different from their parents when they are young 
and on a different line of life, such as caterpillars, 
tadpoles, and other larve; and those which are 
born in the likeness of their parents, but have a 
very distinct youthful period, such as most higher 
vertebrates. He contrasts the various kinds of 
life-history; and shows that in relation to par- 
ticular conditions one chapter is often lengthened 
out and another shortened down. Adult life may 
be condensed into a few days or even hours; it 
may even be lost altogether, as in padogenesis. 
Larval life may be so hazardous, on the other 
hand, that it is all, as it were, telescoped into 
the egg. Part of the tune may be played very 
slowly, part very quickly, and another part left 
out altogether; and all this is, on the whole, 
adaptive, the result of selecting out temporal 
variations in reference to the conditions of life. 
In some cases, perhaps, it works the other way 
round, that a type born, as it were, old, seeks out 
conditions of life suitable for this kind of con- 
NO) 2228, VOL. 93] 
1 
stitution 
parasitism for choice. But our author 
| does not go into this. 
Irom the treasury of interesting things that the 
book contains it is difficult to select, but we may 
refer to three. The first is the masterly treatment 
of the coloration of young animals. Starting 
with the sound idea that the pigments are prim- 
arily by-products of the metabolism, and the 
patterns expressive of growth-rhythms, Dr. 
Chalmers Mitchell shows how in one case they 
are tolerated, and in another toned down, and in 
another specialised. Young animals tend to show 
the more primitive types of coloration—a_ spotti- 
ness, for instance, which corresponds to the par- 
ticulate character of the skin, and while this is 
often very useful, it requires no special utilitarian 
interpretation. Later on, the spots may combine 
into bands and stripes, or the pattern may be 
blurred and toned down, or it may be overlaid by 
a new pattern, often of ruptive vividness, which 
breaks up the natural outlines and makes the 
animal inconspicuous, or forms. startling and 
attractive sex-decorations. It is in interpreting 
the post-juvenile coloration that we must call in 
the aid of the selection theory. 
Another subject well dealt with is the progres- 
sive reduction of the number of offspring. In the 
lower reaches of the animal kingdom there is. pro- 
lific multiplication and high mortality. But it has 
been one of the great steps in evolution to econo- 
mise life by parental care, of which affection is a 
consequence. ‘‘The mere toleration of the young 
by the mother is a new beginning in life, and is 
the foundation of many of the highest qualities 
displayed by the highest animals and by man 
himself. ” The relations of the young to the 
mother “are a continuation of the organic relation 
by which the young are born of the body of their 
mother, and they exist and become, so to speak, 
a habit before the individuality, the physical 
powers, and the senses and aptitudes of the young 
are really awakened.”’ 
Perhaps, however, the most prominent thesis 
of the book concerns the purpose of youth. This 
is in a word self-expression. Why as we ascend 
the scale of being is there this lengthening of the 
period of youth? Why are the young creatures 
fed, protected, freed from care, dowered with 
energy, and given full scope for play? The pur- 
pose of youth is to give time for the breaking 
down of rigid instincts, and their replacement by 
actions controlled by experience and memory—by 
remembered results of experiment. Youth is 
perilous, but the risks run have been justified— 
are continually being justified—in the complexi- 
| fying co-ordinations established by the brain-cells. 
This means the growth of intelligence and the 
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