REVIEWS. 
235 
Finally — After considering to wliat degree of variation individuals of the 
same species are liable, M. de Quatrefages himself thus explains the meaning 
of the term : — “ Species is cm assemblage of individuals more or less resembling 
one another, which arc descended, or may be regarded as being descended, from a 
single primitive pair, by an uninterrupted succession of families.” 
Having thus defined the meaning of the term, the author next brings for- 
ward his evidence to prove that species is immutable ; that is to say, that it 
never has varied since the commencement, and that there can be no transition 
from one species to another. 
He adduces numerous examples in nature in support of this opinion, stating 
that there are trees in existence which must be thousands of years old, and 
which are still precisely similar to individuals of the same species, of recent 
growth. 
Amongst others, he refers to a yew-tree 3,000 years old, and a Boabab- 
tree which is estimated at 5,000 years. 
Another interesting example is found in the discovery of loaves of bread 
in the catacombs of Egypt, containing parts of the wheat-plant, which on 
examination proved to be precisely the same as that now cultivated. 
Nor is the author arrested by the limits of the historic period, for, on the 
authority and experience of Michelet, he mentions the fact that near D61e 
the seeds of a plant, Galium Anglicum, which had been found in the 
Diluvial deposit, had preserved their vitality so far as to germinate, and 
that they had produced plants precisely the same as the existing species. 
Some of the fossil remains of Mammalia, too, that are found in bone- 
caverns show that the animals exactly resembled sjaecies now to be found on 
the surface of the globe. From all these facts, the author concludes that 
species is immutable, and not subject to variation in tune. 
From the consideration of “ species,” he now proceeds to characterize 
“ varieties ” and “ races ” which represent, as it were, the amount of variation 
of which the first-named ( i . e. species) is susceptible. 
We cannot follow him through his discourse, but must be satisfied to 
extract his definition of “ variety” as “an individual, or an assemblage of 
individuals, belonging to the same sexual generation, but distinguished from the 
other representatives of the same species by one or more exceptional characteristics,” 
and that of “race” as “the assemblage of individuals' belonging to one and the 
same species, having received and transmitted by means of generation the 
characters of a primitive variety.” 
In other Avords, according to M. de Quatrefages, a variety is characterized 
by a deviation from the original species, and a race is a variety which has 
multiplied and become permanent — a perpetuated variety in fact. 
These varieties or races are of three kinds : first, those Avhich have acquired 
certain peculiarities through the influences brought to bear upon them by 
nature only, Avithout the intervention of man ; secondly, cultivated varieties, 
in which man has been the modifying agent ; and, thirdly, those varieties 
which, having been subjected for a time to the influence of the human race, 
have escaped and relapsed, as it Avere, into their natural condition. As the 
individuals which Avere originally tamed or cultivated had disappeared, the 
emancipated varieties thus became the representatives of a neAV race. 
All these agencies, however, the author has grouped together under the 
title of “ milieu” or “medium” (meaning thereby the “condition of existence” 
