CHAIN OF ANIMAL LIFE. 501 



in the deep feed upon the vegetation with which 

 to a certain depth it abounds, yet by a wise 

 regulation it is ordered that the greater number 

 prey upon their fellow-occupants of the waters. 

 In consequence of the limits to which marine 

 vegetation extends, it would not have sufficed 

 to sustain the wants of the countless millions 

 of marine beings, had they been confined to a 

 vegetable diet, or had the proportion of preda- 

 cious and herbivorous creatures been in the 

 deep as it is on land, where vegetation almost 

 everywhere abounds. Hence in the ocean 

 generally, and in the polar seas in particular, 

 where the vegetable kingdom which constitutes 

 the support of animal life in milder climates 

 has no representative, if we exclude the minute 

 plants before mentioned, a chain of animal exist- 

 ence has been constituted which as effectually 

 completes the great intention of the preservation 

 of life as that regulating the life of animals on 

 land. Creatures of a higher order prey upon 

 those of a lower, and these again upon those 

 next below them in the scale of created beings, 

 which in their turn feed upon the innumerable 

 infusorial animalcules thronging the ocean. 



The vital function in marine creatures gene- 

 rally, with which the chemistry of the ocean 

 is chiefly concerned, is that of respiration. 

 Although not living in the air, these creatures 



