310 EVOLUTION, OLD AND NEW. 



acquired them, and are transmitted to offspring, with- 

 out the offspring's having itself gone through the pro- 

 cesses of acquisition which were necessary in the case of 

 the ancestor. * Frequent crosses, however, with un- 

 modified individuals, destroy the effect produced. It is 

 only owing to the isolation of the races of man through 

 geographical and other causes, that man himself presents 

 so many varieties, each with a distinctive character. 



" A review of all existing classes, orders, genera, and 

 species would show that their structure, organs, and 

 faculties, are in all cases solely attributable to the 

 surroundings to which each creature has been sub- 

 jected by nature, and to the habits which individuals 

 have been compelled to contract ; and that they are 

 not at all the result of a form originally bestowed, 

 which has imposed certain habits upon the creature, t 



" It is unnecessary to multiply instances ; the fact is 

 simply this, that all animals have certain habits, and 

 that their organization is always in perfect harmony 

 with these habits. \ The conclusion hitherto accepted 

 is that the Author of Nature, when he created animals, 

 foresaw all the possible circumstances in which they 

 would be placed, and gave an unchanging organism to 

 each creature, in accordance with its future destiny. 

 The conclusion, on the other hand, here maintained 

 is that nature has evolved all existing forms of life 

 successively, beginning with the simplest organisms 

 and gradually proceeding to those which are more 

 complete. Forms of life have spread themselves 

 throughout all the habitable parts of the earth, and 

 * ' Phil. Zuol.,' torn. i. p. 259. t Page 260. \ Page 263. 



