1913] Gee: Behavior of Leeches 237 



larly the anterior end, the parent was observed many times 

 twisting itself almost into knots in order to get rid of the young, 

 sometimes very successfully doing so. However, three hours later 

 all of the young were securely attached by their posterior suckers 

 to tlie ventral surface of the body of the parent. This was 

 luidoubtedly accomplished by successive attachment on the part 

 of the young and removal of them by the efforts of the parent, 

 until as its body passed over the young these attached themselves 

 finally in the proper manner and could not be successfully dis- 

 lodged by the parent form. 



Thirteen young, the burden of a single individual, were sepa- 

 rated from their parent and in the dish with them was placed 

 an individual of the same species, which, however, when collected, 

 was found to be carrying no young. The .small leeches attached 

 themselves to this adult quite as readily as to their parent, and 

 upon becoming attached to the foster-parent remained in this 

 position for four days, as long as the experiment was continued. 

 This shows thoroughly that there seems to be present no attraction 

 to the mother, but that any adult specimen, so long as it is a 

 Glossiphonia stagnalis, serves to afford as effective and satis- 

 factory a lodging place as any other of at least the same .species. 



In order to test this point further, thirty specimens in the 

 aquarium were examined to see how many carried young. Out 

 of this number, thirteen carried young, seventeen being without 

 such a burden. The number of young carried liy the different 

 individuals varied from as few as one to as many as twenty-five. 

 Of the thirteen carrying young, two were observed carrying one, 

 and as many carrying three and four respectively. The others 

 carried a larger number. These results indicate no choice of 

 parents within the limit of the species, nor any other alternative 

 on the part of the adult than to carry the young when they 

 become successfully attached to the ventral surface. I have 

 several times observed fair sized young attached to the ventral 

 surface of adults carrying eggs some stages before hatching. 

 Oftentimes the load of a single individual is made up of young 

 of varying sizes, another piece of corroborative testimony. 



This strong positive thigmotaxis of the young is indeed a 

 very adaptive trait, and the persistency with which they will 



