1913] Gee: Behavior of Leeches 243 



and the formation of a new set of collections observed. The 

 young would, in some of the cases, attach themselves to the bodies 

 of other young, a lively squirming resulting in the endeavor of 

 the afflicted specimen to get rid of the imposed burden. The 

 impediment afforded by the attached leech caused a slowing of 

 movement of the specimen carrying the load, and finally a cassa- 

 tion of movement of the two. With this as a starting point, a 

 group of some thirty or forty specimens was formed. In other 

 cases, a specimen moving about would come in contact with the 

 dish where the bottom and sides meet, and the region being one 

 of low light intensity, the young individual would come to rest, 

 and from this as a starting-point a collection would be built up. 

 The position of one of the larger of these groups was so 

 shifted that the young leeches composing it became sub.jected to 

 the influence of strong sunlight. The result was a slow disin- 

 tegration of the collection, many of the animals composing it 

 moving, after a series of random movements, into a less lighted 

 portion of the dish. Some of the individuals remained in the 

 group, however, for a couple of hours in the intense sunlight, 

 failing even to move to a region of less heat and light, the thig- 

 motactie proclivities clearly overcoming the tendency towards 

 negative phototaxis. 



In the groups formed the young were observed to execute 

 undulatory respiratory movements just as did the parent form. 

 No new type of locomotor response, in so far as the free move- 

 ments of the young are concerned, is to be noted in the young 

 as contrasted with the old, though the habit of having thenLseh'es 

 carried around is a trait peculiar to the young. 



Moltschanov (1911) has found in specimens of Glossiphonia 

 and Hemiclepsis that the young when removed from the body of 

 the parent continue to live for only a short time. This obser- 

 vation he cites as evidence supporting the conjecture that the 

 young of these two genera are nourished for a part of their ex- 

 istence by a secretion from the cells of the ventral surface of 

 the parent body. Bolsius (1911) rather refutes this idea and 

 would explain the condition as resulting from insufficient oxygen 

 supply, since the parent form aerates the young during its own 

 undulatorv movements. 



