96 _ Notices of Books. (January, 
but ats energy.” In the fourth chapter (on the “aw aes 
Evolution ’’) we find some curious and most interesting remarks 
on the relative condition of the molecules of carbon, hydrogen, 
oxygen, nitrogen, in organic bodies. It is shown how the mole- 
cules of the first-named element are far less mobile than those 
of the others, since solid carbon has never been expanded into 
the liquid form by the application of the most intense heat, while 
the gases hydrogen, oxygen, nitrogen, have never been condensed 
into the liquid form by the application of the most intense cold, 
accompanied by extremely high pressures. The fifth chapter 
contains a very graphic and comprehensive account of planetary 
evolution and the nebular hypothesis. The next chapter treats 
of the ‘‘ Evolution of the Earth.”’ In discussing the conditions 
of thought and consciousness, the author mentions that conscious- 
ness cannot continue for an instant unless oxygen is in contact with 
the grey tissue of the cerebrum; that mental exertion bears a 
‘‘marked ratio” to the weight of the brain, and to the amount 
of phosphorus contained in it; and, finally, that the amount of 
heat evolved by the cerebrum during the act of thinking varies 
with the amount of mental activity which is taking place. 
The doctrine of Natural Selection is very fully discussed, 
and the chances in favour of its being a true explanation are 
declared to be as many thousand millions to one. When this 
theory is analysed it is found to consist of eleven propositions, 
which may be enumerated as follows :— 
‘‘t, More organisms perish than survive. 
No two individuals are exactly alike. 
3. Individual peculiarities are transmissible to offspring. 
4. Individuals whose peculiarities bring them into closest 
adaptation with their environment are those which 
survive and transmit their peculiar organisations. 
5. The survival of the fittest thus tends to maintain an 
equilibrium between organisms and their environments. 
6. But the environment of every group of organisms is 
steadily, though slowly, changing. 
7. Every group of organisms must accordingly change in 
average character, under penalty of extinction. 
8. Changes due to individual variation are complicated by 
the law that a change set up in any one part of a highly 
complex and coherent aggregate, like an organism, 
initiates changes in other parts. 
g. They are further complicated by the law that structures 
are nourished in proportion to their use. 
10. From the foregoing nine propositions, each one of which 
is indisputably true, it is an inevitable corollary that 
changes thus set up and complicated must eventually 
alter the specific character of any given group of 
organisms, 
N 
