262 LAMARCK, HIS LIFE AND WORK 
tions, seeing that with the aid of much time, of 
changes in local circumstances, in climates, and con- 
sequently in the habits of animals, the progression in 
the complication of their organization and in the 
diversity of their parts has gradually operated (a dé 
Sopérer) in a way that all the animals now known 
have been successively formed such as we now see 
them, it becomes possible to find the solution of 
the following question: 
“What is a speczes among living beings? 
“All those who have much to do with the study 
of natural history know that naturalists at the pres- 
ent day are extremely embarrassed in defining what 
they mean by the word species. 
“In truth, observation for a long time has shown 
us, and shows us still in a great number of cases, col- 
lections of individuals which resemble each other so 
much in their organization and by the exsemdle of 
their parts that we do not hesitate to regard these 
collections of similar individuals as constituting so 
many species. 
“From this consideration we call speczes every col- 
lection of individuals which are alike or almost so, 
and we remark that the regeneration of these individ- 
uals conserves the species and propagates it in con- 
tinuing successively to reproduce similar individuals. 
‘Formerly it was supposed that each species was 
immutable, as old as nature, and that she had caused 
its special creation by the Supreme Author of all 
which exists. 
“ But we can impose on him laws in the execution 
of his will, and determine the mode which he has 
been pleased to follow in this respect, so it is only in 
this way that he permits us to recognize it by the 
aid of observation. Has not his infinite power created 
an order of things which successively gives existence 
to all that we see as well as to all that which exists 
and which we do not know? 
