498 Notices of Books. (October, 
revert to the parental type.” Dr. Bastian has supplemented the 
observations of Pouchet and others, which were said to demon- 
strate the differentiation of the pellicle formed by the coherence 
of bacteria, at the surface of a decomposing infusion, into 
monads, paramecia, &c., by new investigations, tending to show 
that areas of the same pellicle become converted into spores of 
fungi. It is impossible to prove whether there is this conglome- 
ration and conversion of bacteria, or whether the appearances 
are due to developing ova or fungi seen below the film of bacteria. 
In these observations the hypotheses of Archebiosis and Hetero- 
genesis seem inseparably connected ; but not so in the next and 
extremely interesting enquiry that Dr. Bastian takes up. The 
mutability of living forms is acknowledged by all observers, the 
divergence in their views being only a question of degree. 
Those who legitimately doubt that a milk-globule can become 
actually transformed into a penicillium (see p. 311, vol. il., et seq.) 
will find much less difficulty in believing that living matter, 
under various conditions, is able, Proteus-like, to assume an 
endless diversity of forms. ‘The morphological views developed 
by Dr. Bastian are worthy of very attentive study. The work 
concludes with five appendices, containing details of experiments 
and an enquiry concerning ‘‘ The Germ Theory in relation to 
Epidemic and ‘ Specific’ Contagious Diseases.” 
Although we have had occasion to differ from many of the 
author’s conclusions, we are glad to acknowledge that Dr. Bastian 
has made an important contribution to scientific literature, evi- 
dencing wide research and laborious reasoning, and has spared 
no pains to illustrate his meaning by well-executed wood- 
engravings. 
Air and Rain. The Beginnings of a Chemical Climatology. 
By Rosert Ancus Situ, Ph.D., F.R.S., F.C.S., (General) 
Inspector of Alkali Works for the Government. London: 
Longmans, Green, and Co. 1872. 
“WHEN we are children, air is to us nothing.” With this pithy 
little sentence Dr. Smith commences his exhaustive treatise 
upon the constituents of the atmosphere and the results of his 
investigation; and while he shows how especially erroneous is 
the idea of the nothingness of air we entertain as children (and 
not unfrequently by our actions as children of a larger growth do 
we give credit to this idea), he tells us how far we may be 
alarmed, in invading with microscope and chemical test the 
regions around us, by the army of aérial corpuscles and micro- 
cosmic organic matter which our fears may endow with undue 
power. ‘We have,” he says, ‘‘ many people so afraid of this 
organic matter of the air, and of all its floating particles, that 
they would like to filter it all out, and breathe the gases pure. 
We must not allow our fear to go too far. We have no reason 
