244 LAMARCK, AIS LIFE AND WORK 
about the form of its body, the number and condition of 
ats ai # ee the bce which wt get a 
ire ane yore ceeamernees are ‘he two 
principal means which nature employs to give exist- 
ence to all her productions. We know that time 
has for her no limit, and that consequently she has it 
always at her disposition. 
“As to the circumstances of which she has need 
(desoin) and which she employs every day to bring 
about variations in all that she continues to produce, 
we can say that they are in her in some degree in- 
exhaustible. 
“The principal ones arise from the influence of 
climate, from that of different temperatures, of the 
atmosphere, and from all environing surroundings 
(milieux); from that of the diversity of places and 
their situations; from that of the most ordinary 
habitual movements, of actions the most frequent ; 
finally from that of the means of preservation, of the 
mode of life, of defence, of reproduction, etc. 
‘‘ Moreover, as the result of these different influ- 
ences the faculties increase and strengthen themselves 
by use, diversify themselves by the new habits pre- 
served through long periods, and insensibly the con- 
formation, the consistence—in a word, the nature 
and state of the parts and also of the organs—conse- 
quently participate in all these influences, are pre- 
served and propagate themselves by generation ”’ 
(Systeme des Animaux sans Vertebres, p. 12). 
“Tt is: easysfor any. one. to see: that; the ‘habit.of 
exercising an organ in every living being which has 
not reached the term of diminution of its faculties 
not only makes this organ more perfect, but even 
makes it acquire developments and dimensions which 
insensibly change it, with the result that with time 
it renders it very different from the same organ con- 
