PROTRACTILE MOUTHS 



same. When we eat an oyster, a mussel, or a clam, we 

 consume flesh that has been formed out of that of 

 countless tiny beings, living suspended in the water, 

 upon which the shell-fish has fed. And we in our 

 turn feed upon them through this intermediary; we 

 use to our own advantage a form of nourishment of 

 which, otherwise, their very smallness would deprive 

 us. These eaters-of-tiny-scraps thus have a value and 

 a usefulness for us. 



But does this mean that this somewhat scanty 

 sustenance is all that counts in the nutrition of the 

 individual ? Hardly. During their whole existence, a 

 volume of water, enormous in relation to their size, 

 passes through these creatures. This volume is so 

 great that the creature, like the coral polyp, finds in 

 it oxygen to breathe and the calcareous substance of 

 which its thick shell is constructed. Beyond doubt, 

 it also takes other substances, and uses them for the 

 maintenance of its living tissues. The coral polyp 

 feeds like a sea-anemone and its microphagy is comple- 

 mentary. It is assured of a certain minimum of nourish- 

 ment by the water which passes through it. We see 

 this by the way it grows. If the food consists of 

 microscopical particles only, the growth is slow, 

 limited, and reduced to a minimum; if of larger sub- 

 stances, the growth is enhanced and even exaggerated. 



In more complex animals like fishes, food on a large 

 scale become the regular thing. The constantly 

 renewed water serves for breathing but for little 

 more. Fishes move from place to place, their muscles 

 do work, and they need more frequent, more solid, 

 more compact nourishment. Microscopical food would 

 leave their needs incompletely satisfied. Creatures more 

 mobile, almost always more powerful, need stronger 

 and more numerous prey. They are, of necessity, 

 macrophagous, eaters-of-large-morsels, which they must 

 seize, cut up, chew, and digest. They are not neces- 

 sarily superior as " beasts of prey " to the more modest 



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