22(3 



ZOOLOGY 





Fig. 216. — The fauna ot a rapidly flowina stream. In the centre, nets 

 of the caddis-fly ; below, some hydras ; still farther down, a sponge with a 

 leech and a clam (Psidium) left, and a bryozoan (Pectinatella) to the right, 

 J. H. Emerton. 



