VII ANNELIDA 93 



comparatively shallow water. Serpula inhabits deeper water, and 

 dredging is usually necessary to obtain it.^ All these forms 

 flourish in captivity for a time, if supplied with plenty of the 

 microscopic food on which they feed. To ensure this, seaweed, 

 fresh from the sea, should be occasionally rinsed in the water of 

 the tank. It is best, of course, to keep these forms in a tank at the 

 seaside, so that they can be returned to their native haunts after 

 they have been kept in captivity awhile. 



Other Polychaets should be searched for in rock-pools. For the 

 identification of specimens reference should be made to M'Intosh's 

 British Annelids, part ii., which deals fuUy with certain families of 

 Marine Bristle-worms ; also the Cambridge Natural History, vol. ii., 

 should be consulted. 



Horse Leeches may be brought back from a pond and 



kept for a short time, but the fresh-water aquarium in 



which they are put must be carefully covered, otherwise they wiU 



escape. There must be no other inmates of the tank, as the leeches 



wiU attack even fish. 



' Beautiful specimens are obtainable from the Plymouth Biological Station. 



