



*s« 



' «.^ 



14. 



•b 



^■•: 



tftiie 



IMI 

 IT-.. 





1 



• * 



400' 







1 



1 ^ 





1.1 



^ 



it 



# 



1'^' 



Ch. XLII.] 



MPJANS OF EXTINCTION VERY VARIOUS. 



443 



mor 



3 constantly to liannt the other. Thus an intimate 

 connection between the state of the animate creation in a lake 

 or river, and in the adjoining dry land, is maintained; or 

 between a continent, with its lakes and rivers, and the ocean. 



many 



from 



while others, on the contrary, nrged by like wants, forsake 

 their inland haunts, and live on substances rejected by the tide. 



migi 



son supplies another link of the same kind. Suppose the 



number 



grampuses 



the course of a few years the otters at the distance of several 

 hundred miles inland, will be lessened in number from the 

 scarcity of fish. On the other hand, if there be a dearth of 

 food for the young fry of the salmon in rivers and estuaries, 

 so that few return to the sea, the sand-eels and other marine 

 species, which are usually kept down by the salmon, will 

 swarm in greater profusion. 



more 



to prove that the stations of different plants and animals 

 depend on a great complication of circumstances^^ — on an 

 immense varietv of relations in the state of the animate and 



inanimate 



climate 



many 



in order to maintain 



its ground. Many animals feed on 

 certain plants, being often restricted to a small number, and 

 sometimes to one only ; other members of the animal kingdom 

 feed on plant-eating species, and thus become dependent on 

 the conditions of the stations not only of their prey, but of 

 the plants consumed by them. 



How changes in physical geography affect the distribution of 



IS of numerous checks and counter- 

 animal and vep'etable kinp*doms con- 



species 



om 



man 



human 



zoolo- 



gical nor botanical provinces can remain for indefinite periods 



unaltered. 



