244 University of California Publications in Zoology [Vol. 11 



In the dish with some young of Glossiphonia stagnalis I placed 

 a living earthworm, the young leeches being first aroused from 

 the groups which they had formed. The same tendency to hang 

 on as that which enables the young to secure its hold on the 

 mother served in this case to cause it to attach itself to the worm. 

 When the animals became attached to this they fed just as do 

 the older leeches, the outline of the digestive tract standing out 

 a vivid red from the blood contained in it. "When they had 

 become "full" thej' left the worm and formed collections around 

 the edge of the di.sh. Within a few hours after the worm was 

 placed in the dish, of the five or six dozens of young leeches, fully 

 two-thirds of them showed upon examination that they had fed 

 upon the worm. 



These young after having been fed only once in this manner 

 were kept alive with only a few changes of water in the dish 

 for over a month. The fact that this can be done, and that the 

 young leeches perform undulatory movements for respiration 

 themselves, would seem sufficient evidence to dismiss as improb- 

 able the view held by Bolsius (1911) that the death of the young 

 leeches removed from the body of the parent results from the 

 lack of oxygen. Lack of food would seem a more important 

 factor, since with this supplied they are able to live for over a 

 month, or with sufficient trouble can, I believe, be reared to 

 maturity. Whether the food of the young is partly derived 

 from the secretions of the parent as suggested by Moltschanov 

 is a matter which I have not been able to settle. A number of 

 leeches carrying young were supplied with several earthworms 

 as food, and after the parents had fed to satiety the young car- 

 ried on them were examined. Several of them were found to 

 contain blood in their digestive tract. Thus it is probable that 

 the young gain a certain amount of their nutriment in this 

 manner. Also they are undoubtedly able to be separated from 

 their parents by attaching themselves to the food upon which 

 the parent may be feeding, and upon securing a suificiency they 

 may find their way to a place of refuge and comfort upon some 

 other foster-parent which may happen to pass their way. Bolsius 

 (1911) states that he has observed young leeches to leave their 

 parent and find their way back again to the same individual 



