200 
REVIEWS. 
geographical distribution, because of the existing distribution of very- 
analogous species, the length of time that has elapsed, and the im¬ 
possibility of specifically identifying the present vegetation with that 
of the tertiary period. 
“ 6. The theory of a succession of forms being derived from 
earlier ones, is the most natural hypothesis, explaining best the 
known facts of palaeontology, the geographical distribution of plants 
and animals, their anatomy, and their classification; but it wants 
direct proofs, and if true it must have acted so slowly, that its effects 
are appreciable only after a lapse of time long preceding our histo¬ 
rical epochs. 
“ 7. In the present state of science, it is not easier to define a 
species than it is a genus or a family. All the definitions given are 
inapplicable; the worst is that of Linnaeus, who, however, compre¬ 
hended better than any other naturalist the construction of the 
higher groups, varieties, and races, and who gave the name of species 
to that category of groups ; a fact which should oblige us to restrict 
it to the sense he adopted.” 
M. De Candolle is no doubt right in saying that every definition 
of a species is false, though he does not seem to appreciate the fact, 
that it is impossible to define what is (as he everywhere confesses) 
in its origin unknowable and in its essence illimitable ; he is, how¬ 
ever, unintentionally no doubt, unjust to Linnaeus in quoting his 
aphorism, “ Species tot numeramus, quot diversae formae in principio 
sunt creatae,” as his definition of species. If M. De Candolle will refer 
again to the Philosophia Botanica he will find that these “ charac¬ 
ters ” are in no way given as definitions, but are expressions of facts 
in the author’s opinion, and in so far as species were concerned, of 
the opinion of every cotemporary author: it would be as inaccurate 
to call the preceding aphorism a definition, viz., “Eilum ariadneum 
Botanices est Systema, sine quo Chaos est res herbaria,” or that 
again preceding, “ Systema classes per appropriata membra re¬ 
sol vit : classes, ordines, genera, species, varietatesand not only 
are these in no way given as definitions, but the sagacious Swede 
everywhere so obviously avoids attempting the definition of the term 
species, that it is difficult to understand how any one familiar with 
the logical method of Linnaeus’s mind, as evinced in all his writings, 
could attribute to him so grave an error of judgment, as to pro¬ 
pound a statement of fact for a definition. Bor a nearer approach 
to a Linnsean definition we may quote the lines that follow the 
aphorism quoted above, and which involves as good a definition as 
any, and the essence of that so ably expressed by the elder De Can- 
do!le. # Linnaeus goes on, “ Species tot sunt, quot diversas formas, 
* This is to our mind the best definition extant. “Nous reunissons sous le 
nom d’espece tous les individus qui se ressemblent assez entre eux pour que nous 
puissions croire qu’ils ont pu sortir originairement d’un seul etre, ou d’un seul 
couple.”— Phys. Veg. ii. 688. 
