2TO LAMARCK, AIS LIFE AND WORK 
sible to nature, the number of contrary probabilities 
is so enormous that, even philosophically, we can 
scarcely doubt it; for if any species has been pro- 
duced by the modification of another, if the species 
of ass has been derived from that of the horse, this 
could have been done only successively and by gradual 
steps: there would have been between the horse and 
ass a great number of intermediate animals, the first 
of which would gradually differ from the nature of 
the horse, and the last would gradually approach that 
of the ass; and why do we not see to-day the repre- 
sentatives, the descendants of those intermediate 
species? Why are only the two extremes living?” 
(tome iv., p. 390). “If we once admit that the ass 
belongs to the horse family, and that it only differs 
from it because it has been modified (dégéncré), we 
may likewise say that the monkey is of the same 
family as man, that it is a modified man, that man 
and the monkey have had a common origin like the 
horse and ass, that each family has had but a single 
source, and even that all the animals have come from 
a single animal, which in the succession of ages has 
produced, while perfecting and modifying itself, all 
the races of other animals” (tome iv., p. 382). “If it 
were known that in the animals there had been, I do 
not say several species, but a single one which had 
been produced by modification from another species ; 
if it were true that the ass is only a modified horse, 
there would be no limit to the power of nature, and we 
would not be wrong in supposing that from a single 
being she has known how to derive, with time, all the 
other organized beings” (zdzd., p. 382). 
The next sentence, however, translated, reads as 
follows: 
“But no. It is certain from revelation that all ani- 
mals have alike been favored with the grace of an act 
