ZooL.— Vol. III.] STEVENS— CILIATE INFUSORIA. 29 



posterior to the mouth region of a Licnofhora. In a 

 crowded preparation, one Licnofhora was seen to reach 

 repeatedly with a part of the ciha on the left side of the 

 oral disc, aided by flexion of the neck and oral disc, for 

 one of the Boverice, finally seize it and carry it toward the 

 mouth, where it was quickly drawn down into the pharynx, 

 and later passed on into the body like any other mass of 

 food. 



Almost nothing definite can as yet be stated as to the 

 relation of these infusoria to their host. There is no evi- 

 dence to show that they are injurious parasites. So far, no 

 difference has been observed between the condition of the 

 respiratory membrane in individuals containing few or no 

 infusoria, and that in those containing large numbers. 



The structure and some of the movements of Licno^hora 

 have suggested that it might be able to loosen epithehal 

 cells from its host for food, but such regeneration of the 

 epithelium as would naturally follow has not been observed. 



The most probable supposition, at present, is that the 

 infusoria have found here a safe haven where they are con- 

 stantly supplied with fresh sea-water containing an abun- 

 dance of food in the form of diatoms, minute protozoa, etc., 

 supplemented by waste material from the host. 



Where these infusoria come from, and how they pass 

 from the parent to the young holothurian is at present a 

 mystery; for they are found only in the respiratory organ, 

 and no trace of them has been discovered on the surface of 

 this holothurian, on or within other holothurians, or on 

 nudibranchs or worms similar to those on which the other 

 species of Licno-phora live as ectoparasites. Surface towing 

 at various times has also failed to reveal them as free swim- 

 ming forms. A more detailed examination of the habitat 

 of Holothuria californica may, however, clear up these 

 points. 



