132 
NATURE 
[ Dec. 2, 1869 
light of a strictly scientific work, nor is it put forward 
with any pretensions to such a character. Although 
treating of subjects within the domain of their respective 
sciences, it is evidently, and admittedly, zot written for 
the use of either mineralogist, geologist, or metallurgist ; 
it claims but to provide those readers who are not at 
home in mineralogical or geological science, with in- 
formation, arranged in a popular, or, to them, readable 
form, concerning such mineral substances as are likely 
to come under their attention either at home or in the 
course of their travels, and as such we cannot but 
recommend it. 
The worthlessness of coloured illustrations of minerals 
has frequently been descanted upon, and it is perfectly 
true that they can be of no utility whatsoever to the 
student in mineralogy ; in the present instance, however, 
they may be looked upon as but so many ornaments con- 
tributing to the general attractiveness of the volume as a 
whole, We are inclined to the belief that publications 
of this character, without being profound, or even free from 
some not inconsiderable defects, may still do good service 
to the cause of science, by attracting the attention of 
readers who, misled by vulgar report, eschew, without 
trial, what is commonly called the usual dry scientific 
literature ; and that in some instances at least it may 
induce them to follow up their introduction by the study 
of more substantial scientific pabulum. 
DAVID FORBES 
THE ORIGIN OF SPECIES CONTROVERSY 
Habit and Intelligence, in their Connection with the 
Laws of Matter and Force. A Series of Scientific 
Essays. By Joseph John Murphy. (Macmillan and 
Co,, 1869.) 
Il. 
ie his chapter on “ The Rate of Variation,” Mr. Murphy 
adopts the view (rejected after careful examination by 
Darwin) that in many cases species have been formed at 
once by considerable variations, sometimes amounting to 
the formation of distinct genera. and he brings forward 
the cases of the Ancon sheep, and of remarkable forms of 
poppy and of Datura tatula appearing suddenly, and 
being readily propagated. He thinks this view necessary 
to get over the difficulty of the slow rate of change by 
natural selection among minute spontaneous variations ; 
by which process such an enormous time would be 
required for the development of all the forms of life, as 
is incgnsistent with the period during which the earth 
can have been habitable. But to get over a difficulty it 
will not do to introduce an untenable hypothesis ; and this 
one of the rapid formation of species by single variations 
can be shown to be untenable, by arguments which Mr, 
Murphy will admit to be valid. The first is, that none of 
these considerable variations can possibly survive in 
nature, and so form new species, unless they are wsefid 
to the species. Now, such large variations are admittedly 
very rare compared with ordinary spontaneous variability, 
and as they have usually a character of “ monstrosity ” 
about them, the chances are very great against any par- 
ticular variation being useful. Another consideration 
pointing in the same direction is, that as a species only 
exists in virtue of its being tolerably well adapted to its 
environment, and as that environment only changes 
slowly, small rather than large changes are what are 
required to keep up the adaptation. But even if great 
changes of conditions may sometimes occur rapidly, as 
by the irruption of some new enemy, or by a few feet of 
subsidence causing a low plain to become flooded, what 
are the chances that among the many thousands of Josszble 
large variations the one exactly adapted to meet the changed 
conditions should occur at the right time? To meet a 
change of conditions this year, the right large variation 
might possibly occur a thousand years hence. 
The second argument is a still stronger one. Mr. 
Murphy fully adopts Mr. Herbert Spencer’s view, that a 
variation, however slight, absolutely requires, to ensure 
its permanence, a number of concomitant variations, which 
can only be produced by the slow process of self-adapta- 
tion; and he uses this argument as conclusive against 
the formation of complex organs by natural selection in 
all cases where there is no tendency for action to produce 
self-adaptation ; @ fortiorz, therefore, must a sudden large 
variation in any one part require numerous concomitant 
variations ; it is still more improbable that they can 
accidentally occur together ; it is impossible that the slow 
process of self-adaptation can produce them in time to be 
of any use ; so that we are driven to the conclusion, that 
any large single variation, unsupported as it must be by 
the necessary concomitant variations, can hardly be other 
than hurtful to the individuals in which it occurs, and thus 
lead in a state of nature to its almost immediate extinc- 
tion. ‘The question, therefore, is not, as Mr. Murphy 
seems to think, whether such large variations occur in a 
state of nature, but whether, having occurred, they could 
possibly maintain themselves and increase. A calculation 
is made by which the more rapid mode of variation is 
shown to be necessary. It is supposed that the grey- 
hound has been changed from its wolf-like ancestor in 
500 years ; but it is argued that variation is much slower 
under nature than under domestication, so that with wild 
animals it would take ten times as long for the same 
amount of yariation to occur. It is also said that there is 
ten times less chance of favourable variations being pre- 
served, owing to the free intermixture that takes place in a 
wild state ; so that for nature to produce a greyhound from 
a wolf would have required 50,000 years. Sir W. Thomson 
calculates that life on the earth must be limited to some ° 
such period as one hundred million years, so that only two 
thousand times the time required to produce a well-marked 
specific change has, on this theory, produced all the change 
from the protozoon to the elephant and man. 
Although many of the data used in the above calcula- 
tion are quite incorrect, the result is probably not far from 
the truth ; for it is curious that the most recent geological 
researches point to a somewhat similar period as that 
required to change the specific form of mammalia. The 
question of geological time is, however, so large and im- 
portant that we must leave it for a separate article. 
The second volume of Mr. Murphy’s work is almost 
wholly psychological, and can be but briefly noticed. It 
consists to a great extent of a summary of the teachings 
of Bain, Mill, Spencer, and Carpenter, combined with 
much freshness of thought and often submitted to acute 
criticism. The special novelty in the work is the theory 
as to the “intelligence” manifested in organisation and 
