1913] Gee: Behavior of Leeches 235 



from the body is clue to insufficient aeration. The parent with 

 its young attached frequently performs undulatory movements, 

 which provide the young animals with the necessary oxygen 

 supply. 



Castle (1900) has pointed out that in Glossiplionia stagnalis 

 "the time of egg-laying, as well as of spermatophore formation, 

 depends upon the warming of the water in the spring. One 

 can hasten both processes by bringing the animals for a few days 

 into a heated room. ' ' My experience in Berkeley has been much 

 the same. In early December, on January 2, and February 18 

 several dozens of specimens of Glossiphonia stagnalis were col- 

 lected from Stow Lake, Golden Gate Park, San Francisco, and 

 placed in aquaria in the laboratory. These specimens were ex- 

 amined carefully when collected, and were found to carry no 

 eggs or young. After having been in the laboratory for several 

 days the leeches were again examined, and a few of them col- 

 lected at each of these dates were observed to have eggs attached 

 to their ventral surfaces. Specimens collected in the months 

 from August to the middle of November w-ere found many of 

 them to have eggs or young attached. This would indicate that 

 the lower temperatures cause the cessation of breeding. A some- 

 what extensive breeding season would seem necessary to account 

 for the literal millions of specimens of this species inhabiting 

 the stones along the edges of this lake, in the shallower water. 



The fact that a form as low in the scale of life as the leech 

 is to be found carrying eggs in the same manner as does Glossi- 

 phonia naturally arouses the question as to the possible occur- 

 rence of a "parental instinct" in its simpler expressions. Several 

 individuals of Glossiphonia were secured carrying eggs attached 

 to the ventral surface. These eggs were contained in sacs, as 

 described by Castle (1900), some four to six usually, and totaling 

 a varying number from twenty-one to thirty, with sometimes a 

 few more. With a blunt-pointed needle these sacs of eggs were 

 removed, and immediately placed, together with the individual 

 from which they were taken, in a small glass dish 3 cm. in diam- 

 eter. Careful count was made of the eggs separated in order 

 to prevent any error which might arise through the laying of 

 more eggs. When coming in contact directly with the eggs the 



