^^^^^ Gee: Beliavior of Leeches 241 



discussed in a later portion of this paper. On the other hand, 

 hunger, by producing a condition of increased irritability in 

 the organism, would tend within certain limits to cause activity 

 resulting in what might be called a search for food. 



3. Behavior op the Young Leeches 



Tlie reactions of the young of Hemiclepsis and Glossiphonia 

 when only about two millimeters in length are, with few excep- 

 tions, essentially the same as those of the adult specimens. The 

 normal activity of the young is marked by a somewhat greater 

 irritability than is the case in the older forms. This fact is 

 very clearly indicated in the excess of random movements in the 

 process of locomotion of the young. The response given by the 

 young to localized contact stimuli are the same as those described 

 for the adult forms in a previous portion of this paper. 



The positive thigmotaxis, so well developed in the adult 

 leeches, is even more pronounced in the young individuals of 

 the two genera studied. This is shown to a marked degree in 

 the young of Hemiclepsis. It was unfortunate that only one 

 specimen of this species carrying young could be secured ; how- 

 ever, the forty-three composing its burden provided a sufficient 

 number to permit of the observation of many features of their 

 behavior. When removed from the body of the parent, and 

 placed in a separate dish, the young would usually cluster in one 

 or two groups, their posterior suckers attached side by side to 

 the bottom of the dish. In such a position the young were al- 

 lowed to remain for a couple of weeks. They were observed 

 rather frequently during the day, and sometimes in the evenings. 

 So ff.r as noted, scarcely a single specimen released its hold on 

 the substratum. The slightest jar of the table would set them 

 to waving their anterior ends about in the dish, as if searching 

 for the intruding factor. Soon, however, they would again settle 

 down to a comfortable repose. This grouping, in so far as rela- 

 tive position of the bodies of the young to each other is con- 

 cerned, is practically the same as that which is found among the 

 young while attached to the under surface of the body of the 

 parent. 



