66 



FOOD 



They suck the blood and other juices of the male, for they 

 also have minute mouths. 

 When we come to the 

 vertebrates, we find their 

 food is as diverse as is that 

 of the Invertebrata. The 

 ultimate food of fishes is 

 the innumerable minute, 

 unicellular, green algae, 

 known as Diatoms. These 

 organisms float near the 

 surface of the waters, and 

 in sunlight are enabled to 

 build up their bodies from 

 water and carbon dioxide 

 dissolved in both sea- and 

 fresh-water. Diatoms are 

 eagerly devoured by in- 

 credible numbers of small Crus- 

 tacea, largely by the Copepoda, 

 and these minute Crustacea thus 

 form a second stage in the food of 

 fishes. Many of these Copepods are 

 of surpassing beauty, as beautiful 

 as birds-of-paradise or Mr Brock's 

 fireworks. Yet they are hardly vis- 

 ible to the naked eye. The Crustacea 

 are, as regards numbers, the pre- 

 dominant inhabitants of the sea, 

 exceeding any other group of marine 

 animals. Some of them live at the 

 bottom of the sea and some on the 

 sea-shore, and one small group of 

 minute size, the Ostracoda, act as j^^ igr^derview of an Indian 

 scavengers, consuming the dead scor-pion, Scorpio swammerdami. 

 bodies of other animals. All form ^rom Shipley and MacBride. 

 foodforfishcs. Belowthe limit of the * ''^^- ^'^^^ 

 penetration of sunlight, which is at the very most about 300 

 fathoms — for the most delicate pan-chromatic plates register 



