Planariidae 153 



the worms, the length of the piece cut off depending upon the size of the 

 worm. We separate these tail pieces into pans by themselves and allow 

 them to stand without feeding for a period of 4 weeks, at which time 

 they have attained the adult shape and are ready for nutritional ex- 

 periments. 



We keep our experimental worms in an incubator with a temperature 

 of 24 C, but the stock and regenerating worms are kept in the labora- 

 tory with the heat turned on at night during the cold season. If the 

 worms become thoroughly chilled many or all of them will die. This 

 happens above the freezing point and makes it wisest to keep the stock 

 pans away from cold windows. 



PLANARIA 



William LeRay and Norma Ford, University of Toronto 



FOR eight years a culture of Planaria [=Euplanaria] maculata has 

 been kept under observation and fed very successfully with enchy- 

 traeid worms. The animals were collected in a large pond and a selec- 

 tion was made of the individuals which would accept the enchytraeid 

 worms as food. 



The planaria are kept in a wooden tub (24 inches in diameter and 

 n inches deep), charred on the inside, and are fed about once a week. 

 Approximately 2000 individuals are maintained in this space. When 

 fed, a level teaspoonful of worms is dropped over the bottom of the 

 tub. Several planaria will cluster over each worm and so share the food. 

 The amount of food given is regulated by the growth of the planaria: 

 if they are getting smaller, more enchytraeid worms are offered; if more 

 individuals are needed, additional food will speed up their growth and 

 reproduction. 



When large numbers of planaria are needed for class material, we 

 are careful not to disturb the tub for two or three days. A film then forms 

 over the surface of the water. To bring the planaria to the surface, the 

 sides of the tub are tapped with a hammer. Each animal is then picked 

 out with a fine glass rod which is slipped under its dorsal side as it floats 

 ventral side up. The planaria folds its dorsal surface around the rod 

 and it is then dropped quickly into a dish for study. Without the film 

 on the surface of the water the planaria will not stick to the rod. 



COLLECTION AND CULTURE OF PLANARIA 



George R. La Rue, University of Michigan 



BAITING for planaria by the method described by Hyman (Trans. 

 Amer. Micr. Soc. 44:79, 1925) may not always be practicable. 

 Planaria often occur in abundance, sometimes by hundreds, on the lower 

 surface of stones or submerged boards in swiftly flowing water below 



