312 FAMILY: TRYPANOSOMIDiE 



Selenomastix ruminantium, realizing that it was the same as the organism 

 described by Certes. Prowazek's name evidently has priority, as the 

 organism certainly does not belong to Kent's genus Ancyromonas. Da 

 Cunha (1915) noted the organism in the caecum of guinea-pigs, as did 

 also Fonseca (1916) and Simons (1920, 1921). The form in the guinea-pig 

 was described in detail by Boskamp (1922). The body of the organism 

 is a rigid crescent measuring 6-8 to 9-1 by 1-8 to 2-3 microns. A bunch 

 of flagella springs from the hollow of the crescent, near which is a 

 deeply staining mass. Reproduction is by transverse fission through the 

 flagellar region. Half the flagella pass to each daughter individual. 

 Boskamp believes that the organism is not a Protozoon, but is related to 

 the Spirilla. The writer has seen the organism in large numbers in the 

 caecum of a guinea-pig in England. It seems quite possible that Fonseca's 

 Callimastix is a rounded form of the same or a similar organism. 



2. Family: TRYPANOSOMID^ Doflein, 1901. 

 In this family are grouped a number of closely related flagellates. They 

 are the true trypanosomes typically seen in the blood of vertebrates or 

 their invertebrate hosts; the leptomonas, crithidia, and herpetomonas, 

 which have only an invertebrate host, in which they live mostly as intestinal 

 parasites; the leishmania, which, like the trypanosomes, have both a verte- 

 brate and an invertebrate host, though the latter is not definitely known; 

 and the phytomonas, which have both an invertebrate and plant host. 



RELATION OF VARIOUS TYPES TO ONE ANOTHER. 



All the members of the family resemble one another in the possession 

 of a nucleus and a single flagellum which arises from a composite structure, 

 the kinetoplast (Fig. 150). The latter is made up of a posterior deeply 

 staining body, the parabasal, and an anterior blepharoplast in which the 

 axoneme of the flagellum has its origin. The kinetoplast, or the parabasal 

 alone, is often termed the kinetonucleus, a name proposed by Woodcock 

 (1906), while Laveran and Mesnil, in their writings, refer to it as the small 

 nucleus or centrosome. It is also called the micronucleus, a name which 

 should not be employed, for it is used to designate one of the highly 

 specialized nuclei of the Ciliata. The term kinetonucleus implies that it is 

 equivalent to a nucleus, and in this sense is misleading. On this account 

 the term kinetoplast, first employed by AlexeiefE (19176) for the corre- 

 sponding structure in Bodo caudatus, will be used here. The portion of the 

 axoneme or axial filament of the flagellum between the blepharoplast and 

 the surface of the body where the flagellum commences is often called 

 the rhizoplast, but this term has been used for many different fibrils. The 

 body of one of these flagellates usually consists of an elongated, flattened, 



