448 CONCLUDING REMARKS. 



served to result, it is ever traceable to the individuals 

 which are paired, being similarly wanting in full struc- 

 tural integrity. 



d. Another of the modes of Man's Selection, which 

 vary the evil results of Interbreeding, is that mode 

 which re-develops only one of the lost or reduced 

 characters of the species; the several varieties of each 

 such species being formed by the mere retention of each 

 variety at a different stage of the exclusive develop- 

 ment of this one character. 



This process of Selection is principally exemplified 

 in the case of Plants, there being, in each species, gen- 

 erally only one character which Man values, and to 

 which exclusively he devotes his attention. In one 

 species, it is, perhaps, the fruit alone which he prizes ; 

 in another, it is the flower; in another, the leaves; in 

 another, the roots, &c. The extreme development of 

 this one, valued feature, and the reduction, both positive 

 and relative, of the other characters of the species, have 

 sensibly modified the normal structure of the Plants. 



In consequence of this modification of the structural 

 integrity of Plants, there is observed to be an injurious 

 modification of the physiological integrity, which re- 

 veals itself when the Plants are self-fertilized, or when 

 two individuals, similarly modified, are interbred; loss 

 of fertility, loss of constitutional vigor, and sterility 

 being the outcome of such self-fertilization, or of such 

 interbreeding, in proportion to the degree in which the 

 parents similarly depart from the full, structural integrity 

 of their species. 



All of the species under domestication furnish con- 



