The Relation of Shellfish to Fish in Oneidu- Lttke 15 



shells, bits of sticks, plants, etc., crawl over the bottom, the 

 caddis-fly larvae dragging with them the houses that protect 

 their soft bodies. Water bugs. Water Boatmen, beetles, both 

 adult and young, and many kinds of small snails complete 

 the variety of this wealth of animal life on the bottom (see 

 Figures 11-13). 



On the rocky shores the clams live between the stones, 

 partly buried in the sand or gravel, and crawfishes of many 

 ages and sizes hide beneath the rocks ready to retreat from 

 foe or to pursue some prey ; on the stones many snails live, 

 associated with the young of May-flies (Heptagenia) , the 

 flat, disc-like larva or young of a beetle (Psephenus), and 

 the Spiral Caddis-fly larva (Helicopsi/clie) which makes its 

 case of sand grains so nearly in the form of a spiral snail 

 shell as to confuse, many years ago, one of America's fore- 

 most students of mollusks (see Figure 1-i). The stones on 

 many points of land are coated with sponges, which look 

 like great patches of green velvet through the water. 



The plants, too, afford a resting place as well as a foraging 

 ground for many animals, and we find on the leaves of the 

 \vater-lilies the small limpit-like snails (Ancylus), the round 

 shells of the Orb Snails (Planorbis) and the Tadpole Snails 

 (Physa), associated with young and full-grown beetles, 

 aphids or plant lice, and the curious caterpillars of moths 

 (Nymphula) which make cocoons on the surface of the lily 

 leaves. If we examine the leaves of the bulrush, even in 

 water six feet deep, we find them covered w r ith the little 

 brown Hydras, the long tentacles of which are outstretched 

 to catch unwary protozoans or other minute animals that 

 may chance to drift that way. Many of the bulrush stems, 

 as well as the other plants, are encrusted with the little cases 

 of the moss-animals or bryozoans, appearing indeed as though 

 a brow r n moss. Amid this great wealth of animal life it is 

 not strange that fish find an attractive environment where 

 food is 'plentiful and conditions are favorable for their 

 growth and breeding. 



