36 Universitij of California Publications in Zoologii [Vol. 20 



ENCYSTMENT 

 Associated with the vegetative and fission stages of Trichomitus 

 in a few hosts but not all, we have found many small individuals 

 (pi. 4, figs. 24, 29-33) in which binary fission is occurring and in 

 which there is a tendency for the body to round up into a spheroidal 

 or ellipsoidal mass. These small sizes may result from rapid fission 

 without compensating growth or from plasmotomy of part of the cyto- 

 plasm. In these same hosts occur also numerous ellipsoidal cysts 

 about 13 by 2Q/i with a deeply stained netwoi'k with thickenings at 

 the nodes spread over the surface (pi. 4, figs. 26, 27). The cyst wall 

 is double and the network is due to the accumulations of some stainable 

 substance between the walls. Within the cyst is a single individual 

 (pi. 4, fig. 31) with a very long parabasal and undulating membrane 

 making nearly two complete coils, such as might result from the coiling 

 up of an individual with abnormally large neuromotor system (pi. 4, 

 fig. 30). In other cases two such individuals (pi. 4, fig. 26) are found 

 within the cyst. This might result from encystment after or during 

 mitosis but prior to plasmotomy. Such cysts may facilitate the carry- 

 ing over of infection from one individual host to another. They have 

 all the indications of being resistant stages. 



EELATIONSHIPS 

 This is a species of Trichomitus, a genus founded by one of us 

 (Swezy, 19156) for the reception of a minute and simple triehomonad 

 from amphibians. In its vegetative phases the form here described 

 has the morphological features of Trichomitus parvus Swezy, namely, 

 three anterior flagella, undulating membrane, parabasal, and no axo- 

 style. It differs greatly in size, in the massive development of the 

 parabasal, and at mitosis in the distinct separation of centrosome and 

 blepharoplast. Binary and multiple fission were followed in the species 

 from amphibians but no trace of such separation was detected. 



Such a difference as this might justify generic separation but it 

 might be impracticable to apply it in future diagnosis of any species 

 of the genus which may come to light. The difference is, however, of 

 such morphological import as to justify subgeneric separation. We 

 accordingly a.ssign it to 



Trichomitopsis subgen. nov. 

 Trichomitus with centrosome separated fi"om blepharoplast at 

 mitosis. T.ype species Trichomitus termitidis sp. nov. from 

 Termopsis angusticoUis Walker. 



