FUNDAMENTAL RELATIONS OF ANIMALS 123 



balance which either of them would singly disturb to a certain 

 degree. The common agricultural practice of manuring exhibits 

 from another side the dependence of one kingdom upon the other: 

 the undigested particles of the food of animals return to the ground 

 to fertilize it for fresh production. Again, the whole animal king- 

 dom is either directly or indirectly dependent upon the vegetable 

 kingdom for its sustenance, as the herbivorous animals afford the 

 needful food for the carnivorous tribes. We are too far from the 

 time when it could be supposed that Worms originated in the decay 

 of fruits and other vegetable substances to need here repetition of 

 what is known respecting the reproduction of these animals. Nor 

 can it be necessary to show how preposterous the assumption would 

 be that physical agents produced plants first, in order that from 

 these, animals might spring forth. Who could have taught the physi- 

 cal agents to make the whole animal world dependent upon the 

 vegetable kingdom? 



On the contrary, such general facts as those above alluded to 

 show more directly than any amount of special disconnected facts 

 could do the establishment of a well-regulated order of things con- 

 sidered in advance; for they exhibit well-balanced conditions of 

 existence, prepared long beforehand, such as only an intelligent 

 being could ordain. 



SECTION XXX 

 PARASITIC ANIMALS AND PLANTS 



However independent of each other some animals may appear, 

 there are yet many which live only in the closest connection with 

 their fellow-creatures and which are known only as parasites upon 

 or within them. Such are the intestinal Worms and all the vermin 

 of the skin. Among plants the Mistletoe, Orobanche, Rafflesia, and 

 many Orchideae may be quoted as equally remarkable examples of 

 parasitism. 



There exists the greatest variety of parasites among animals. It 

 would take volumes to describe them and to write their history, 

 for their relations to the animals and plants upon which they are 



