THE FREE-LIVING FLATWORMS (TURBELLARIA) 331 



sometimes find them in greenhouses and gardens, under flower 

 pots or boxes, in moist woods under bark and old logs, or in any 

 moist sheltered place. They are easily overlooked because of the 

 similarity in their appearance to young snails. 



Rhabdocoels are especially abundant in pools or ponds which 

 contain much algal or other vegetation. A lens is often neces- 

 sary to distinguish them from other minute organisms. They 

 may be collected by means of a Birge net or other apparatus used 

 in collecting small animals or simply by gathering carefully plant 

 material, sediment, or debris from the ponds where they live 

 and exposing this material in shallow dishes in the laboratory. 

 The larger triclads are easily collected as they cling to the stone 

 or leaf which conceals them when it is lifted from the water and 

 they may then be removed with the point of a knife, or washed 

 off into a large-mouthed jar. When algae or debris which con- 

 tains them is disturbed, they contract, remain motionless until 

 the disturbance ceases, and then come to the surface and crawl 

 about excitedly, thus being easily picked up with a large-mouthed 

 pipette. 



Most Turbellaria are easily kept in cultures if the water is kept 

 pure. Rhabdocoels should have a supply of unicellular and tila- 

 mentous algae such as diatoms, Spirogyra, etc., and small animals 

 like rotifers, Crustacea, and insect larvae, as they use both plant 

 and animal food. Planarians are largely, if not entirely, carnivo- 

 rous and thrive in aquaria which are supplied with running water 

 so that they may be given a constant supply of food. If this is 

 not possible, they may be kept in ordinary aquarium jars or shal- 

 low dishes with or without algae. They will live for weeks with- 

 out food but become greatly reduced in size. They take food 

 readily, especially at night, and should be fed once or twice a 

 week on earthworms, snails, liver, or almost any soft fleshy animal 

 tissue. The water should be changed after each feeding. 



Small forms are easily studied under the microscope if slightly 

 compressed by the cover glass through the absorption of the 

 surplus water with filter paper. A few quince seeds added to 

 the water are of great assistance as they form a jelly which re- 

 tards movement without injury to the animal. Cells or hollow 



