1/4 HEROES OF SCIENCE. 



of mere varieties in order to form characters for 

 what we choose to call a species, and sometimes we 

 are induced to pronounce individuals, but slightly 

 differing, and which others regard as true species, 

 to be varieties. The greater the abundance of 

 natural objects assembled together, the more do we 

 discover proofs that everything passes by invariable 

 shades into something else ; that even the more 

 remarkable differences are evanescent, and that 

 nature has, for the most part, left us nothing at our 

 disposal for establishing distinctions save trifling, 

 and in some instances puerile, peculiarities. We 

 find that many genera amongst animals and plants 

 are of such an extent, in consequence of the number 

 of species referred to them, that the study and 

 determination of these last has become almost im- 

 practicable. From a great number of facts we 

 learn, wrote Lamarck, that in proportion as the 

 individuals of one of our known species change 

 their situation, climate, and manner of living, they 

 change also little by little, the consistence and 

 proportions of their parts, their form, their facul- 

 ties, and even their organization, in such a manner 

 that everything in them comes at last to participate 

 in the mutations to which they have been exposed. 

 Even in the same climate, a great difference of 

 situation and exposure causes individuals to vary ; 

 but if these individuals continue to live, and to be 

 reproduced under the same difference of circum- 

 stances, distinctions are brought about in them 

 which become in some degree essential to their 



