DEC EN ERA TION. 



that by the aid of this green substance they feed on 

 carbonic acid, making starch from it as plants do. 

 As a consequence we find that their stomachs and 

 intestines as well as their locomotive organs become 

 simplified, since they are but little wanted. These 

 vegetating animals, as Mr. Geddes calls them, are the 

 exact complement of the carnivorous plants, and show 

 how a degeneration of animal forms may be caused 

 by vegetative mttrition. 



Another possible cause of degeneration appears 

 to be the indirect one of minute size. It cannot be 

 doubted that natural selection has frequently acted 

 on a race of animals so as to reduce the size of the 

 individuals. The smallness of size has been favour- 

 able to their survival in the struggle for existence, 

 and in some cases they have been reduced to even 

 microscopic proportions. But this reduction of size 

 has, when carried to an extreme, resulted in the loss 

 or suppression of some of the most important organs 

 of the body. The needs of a very minute creature 

 are limited as compared with those of a large one, 

 and thus we may find heart and blood-vessels, gills 

 and kidneys, besides legs and muscles, lost by the 

 diminutive degenerate descendants of a larger race. 



E 2 



