752 The American Naturalist. [August, 
escape the researches of the histologists and embryologists. While 
using the many important and essential facts brought to light by the 
latter class of investigators, he has not neglected researches which do 
not require the mechanical appliances which give a somewhat factitious 
value to the pursuits of microscopy and telescopy. Prof. Eimer is 
already well known through his important investigations on the dis- 
tribution and origin of color-markings in insects and reptiles; his 
discussion. of the variations of the wall lizard of Europe (Lacerta 
muralis) being a model of this kind of work. From these and similar 
researches on the variations in the colors of caterpillars, and imagines 
of various Lepidoptera, he has shown conclusively that color-variations 
are not promiscuous or fortuitous, but follow certain definite directions. 
This result is in entire harmony with those derived from similar studies 
which I have made on the coloration of certain snakes, and of which 
I have published, especially the case of the North American Ophibolus 
doliatus.2 The author then proceeds to discuss the effects of physical 
agencies as causes of variations, as light, temperature, humidity, etc. 
Of the effects of use and disuse he says (p. 153): “It isa self-evident 
physiological fact that practice or use strengthens and improves the 
organs of the body, while disuse causes them to deteriorate." He 
then adds: ‘That characters acquired through use or disuse are in- 
herited, and must therefore aid in the formation of new species, can be 
proved more easily than any of the propositions I am maintaining. If 
I were to bring together all the facts which could be used as evidence 
on this point, I should never come to the end of them, for I should 
have to refer to all the facts of anatomy and physiology. But I intend 
to show in particular that use and disuse by themselves must lead to 
the formation of new permanent characters, without the aid of selec- 
tion, for even this I hold to be a physiological necessity." Accord- 
ingly, the author cites many facts in support of this view. Among 
these he relates some interesting cases of the inheritance of mutilations 
and abnormalities. 
Considerable space is devoted to the question of the origin and 
transmission of mental characteristics, and here especially Prof. Eimer 
shows himself an acute observer and thinker. His residence has 
grounds attached to it, where he has been accustomed to have under 
his eye animals both domestic and wild, and his observations on the 
habits of these are highly interesting. He coincides in opinion with 
most observers on this subject, that mental habits are readily trans- 
mitted by inheritance, and his observations on young chickens and 
other birds are very instructive, 
? Proceeds, U. S. National Museum, 1888, p. 381. Bulletin do., I. 1875, p. 3. 
