756 Notices of Books, [November, 
as the conger, the sprat, the horse-mackerel and the John 
Dorey. 
We trust that the Royal Society of Tasmania will persevere 
in the course that it has evidently taken, working out the biology, 
geology, mineralogy, and climatology of the island. 
Colour-Blindness ; its Dangers and its Detection. By B. Joy 
Jeffries, M.D. Boston: Houghton, Osgood, and Co. 
London : Triibner and Co. 
Dr. Jeffries had, it appears, originally intended to produce an 
English version of the work of Prof. Holmgren, “ Colour- 
Blindness and its Relations to Railroads and the Marine.” Being, 
however, anticipated by an abridged translation which appeared 
in the Reports of the Smithsonian Institute, he was led to draw 
up an independent treatise, covering, however, essentially the 
same ground. It must therefore be distinctly understood that 
the present volume is not, and does not profess to be, an ex- 
haustive monograph of colour-blindness. The author’s aim is 
essentially practical. He seeks to point out the dangers to life 
and property which may arise from the employment on railways 
or on shipboard of men defective in the colour-sense, and to 
explain in detail the best means for their detection. These dan- 
gers are undoubtedly real and serious. If one out of every 
twenty-five of the male population of civilised Europe and 
America is more or less unable to distinguish colours,— a truth 
which appears established, — there is a certain element of proba- 
bility that the engine-driver or the look-out man, upon whose 
judgment our personal safety depends, may mistake the colour 
of a signal and rush headlong to his own and our destruction. 
The more speculative, and to many men of Science the more 
interesting, phase of the subjeCt, is but slightly touched upon. 
Little new light is thrown upon the ultimate causes of colour- 
blindness; upon the laws of its production by accident, disease, 
or immoderate narcotism ; upon the rationale of its predomi- 
nating frequency in the male sex, its relative occurrence in 
different races and nations, and its possible extension among the 
lower animals. The comparative delicacy of the colour-sense 
among the two sexes in birds, &c., becomes a very important 
point. If, as among mankind, the females are the most sensitive 
to colour, whilst the males are admittedly the most highly 
coloured, we have a strong confirmation of the hypothesis of 
sexual selection. 
Nor does Dr. Jeffries discuss the alleged recent development 
of the colour-sense, nor the influence which its varying degrees 
of perfection may have upon decorative art or upon personal 
