1890.] Recent Literature. 927 
Poulton on the Colors of Animals.'—The meaning and uses ot 
animals are stated systematically in this monograph, a valuable ee 
to the literature of this department of natural history. The c 
tion shows an intimate knowledge of the subject from personal zo 
tion and a wide acquaintance with the studies of others, whether 
embodied in occasional papers or the proceedings or transactions of 
various scientific societies. Mr. Poulton adopts the general title, 
« The Colors of Animals," in order to indicate the contents of this 
volume, although the majority of the examples are taken from insects, 
chiefly from a single order, the Lepidoptera. 
In investigating the physical cause of animal colors, their produc- 
tion is conveniently grouped under two heads, —pigmentary and 
structural, The first includes, under a first head, colors caused by 
absorption, the effects varying with the chemical nature of the sub- 
stance (pigment). The second head includes the colors produced in 
all other ways, the efficient cause being the structure of the substance 
rather than its chemical nature. No pause is made to discuss the 
details of the causes of color by absorption, except to. mention the 
observance of vibrations of very different rates. The existence of 
vibrations of light above and below the visible series is proved in 
other ways, and reference is made to the conclusion reached by Sir 
John Lubbock (** The Senses of Animals’’) that it is certain that some 
animals can see vibrations which do not affect our eyes. "The slowest 
vibrations that we can see produce the effect of red ; the most rapid, 
the effect of violet; **while the intermediate vibrations cause the 
other well-known colors of the rainbow or the spectrum.’ 
The white markings of animals are produced in various ways. The 
writer explains the snow-like appearance of white hairs and feathers by 
the number of minute bubbles of gas which are contained in their 
interstices. ““Interference colors," due to thin films of air in- 
cluded between layers of horny consistence, are then treated with 
" reference to their probable production of iridescent coloring. In 
some cases it is supposed that the chinks between the layers of tissue 
are kept open by films of liquid, producing the brilliant metallic ap- - 
pearance of many chrysalides. An interesting observation showed a 
brilliant golden beetle lost all its lustre after hibernating in captivity, 
but entirely regained it after drinking some water. After brief con- 
sideration of the colors due to diffraction and refraction (prismatic 
1 The Colors of Animals, their meaning and use, especially considered in the case 
of insects. By Edward Bagnall Poulton, M.A., F.R.S. jas chromo-lithographic 
and 66 figures intext. New York: D. Appleton 
