LAMARCK’S THEORY OF EVOLUTION 233 
tions which would prevent any one from misunder- 
standing them.”” It may be inferred from this that 
he had for some time previous meditated on this 
theme. It will now be interesting to see what factors 
of evolution Lamarck employed in this first sketch of 
his theory. 
After stating the distinctions existing between the 
vertebrate and invertebrate animals, and referring to 
the great diversity of animal forms, he goes on to 
say that Nature began with the most simply organ- 
ized, and having formed them, “then with the aid 
of much time and of favorable circumstances she 
formed all the others.” 
“It appears, as I have already said, that ¢zm#e and 
favorable conditions are the two principal means 
which nature has employed in giving existence to all 
her productions. We know that for her time has no 
limit, and that consequently she has it always at her 
disposal. 
“As to the circumstances of which she has had 
need and of which she makes use every day in order 
to cause her productions to vary, we can say that 
they are in a manner inexhaustible. 
“The essential ones arise from the influence and 
from all the environing media (w2/zeux), from the 
diversity of local causes (diversité des lieux), of habits, 
of movements, of action, finally of means of living, 
of preserving their lives, of defending themselves, of 
multiplying themselves, etc. Moreover, as the result 
of these different influences the faculties, developed 
and strengthened by use (wsage), became diversified 
by the new habits maintained for long ages, and by 
slow degrees the structure, the consistence, in a word 
the nature, the condition of the parts and of the 
organs consequently participating in all these influ- 
