ZooL.— Vol. III.] STEVENS -CILIATE INFUSORIA. 5 



made with a view to confirm Biitschli's theory, that Licno- 

 pkora is an intermediate form between hypotrichous and 

 peritrichous CiHata. For this purpose, careful observations 

 were made of both anatomical and cytological structure, 

 special attention being given to the method of division of 

 Licnofhora. The results of Wallengren's observations lead 

 him to discard Biitschli's theory and to look upon Licno- 

 ■phora as a highly specialized form of the Peritricha. Its 

 relationship to other genera of peritrichous infusoria is, in 

 his opinion, still an open question. 



Habitat. — The species of Licno-phora, which is the sub- 

 ject of this paper, is an entoparasite or commensal of Holo- 

 thuria californica. It occurs in large numbers in the 

 respiratory tree of the holothurian, and has not yet been 

 found as an ectoparasite on the same or other hosts in 

 Monterey Bay. When the respiratory tree, just removed 

 from the holothurian, is examined under a low power, the 

 LicnophorcB are seen attached to the inner epithelial sur- 

 face of the transparent membrane, in company with a second 

 ciliate infusorian to be described in the second part of this 

 paper. 



The number of both forms varies greatly in different 

 individuals. Out of the many holothurians examined (one 

 hundred or more), only one was without these parasites. 

 One contained only the second form; a few had only a few 

 specimens of Licnophora; but an abundance of both was 

 the rule. The material was much richer in 1899 than it 

 was in 1898. The infusoria occurred in largest number in 

 the peripheral branches of the respiratory tree, and in gen- 

 eral at the tips of the finger-like subdivisions. 



The habitat of this species is peculiarly fortunate for 

 cytological study on account of the abundance of material 

 and the ease with which large numbers of individuals can 

 be fixed, imbedded, sectioned, stained, and mounted in 

 series. 



General Description. — Like the other species, Licno- 

 fhora macfarlandi has an elongated body consisting of 

 three distinct regions — an oral disc, an attachment disc, and 



