TKYPANOSOMIDyE 57 



Two varieties of Trypanosomidse are met with in fish. Of these, 

 one, the Trypanosoma, is furnished with a single flagellum attached to 

 an undulating membrane, and closely resembles the Trypanosome of 

 mammals (fig. 13). The second, Trypanoplasma, is generally the 

 more numerous. In it the undulating membrane is prolonged into 

 a short flagellum at the hinder end of the body, and the organism 

 is furnished with another long and quite free flagellum (fig. 14). 

 These parasites are easily recognized, even with a low-power lens, 

 by their active darting movements, by which the red cells in their 

 neighbourhood become displaced. 



When examining fresh material, the student should first note the 

 characteristic movements, which differ somewhat in the two varieties, 

 and should then endeavour to make out something of the structural 

 peculiarities. In the Trypanoplasma the flagella are placed close 



FIG. 14, Trypanosoma cyprini. Four 

 examples between red corpuscles from 

 FIG. 13. Trypanosoma gambiense, Button, the blood of carp. (After Plehn and Hofer, 

 from the blood of man. Magnified about from Braun.) The long free nagellum is 

 1,700 : 1. (After Dutton, from Braun.) placed at the anterior end of the parasite. 



together at the anterior end of the organism ; they proceed from two 

 contiguous basal structures, behind which lies a long spindle-shaped 

 flagellar nucleus. The round principal nucleus lies also in the front 

 part of the body, opposite to the flagellar nucleus. In the Trypano- 

 soma, however, the principal nucleus generally lies in the middle of 

 the body, while the flagellar nucleus, which is a good deal smaller in 

 size, is placed near the non-flagellate end. Close to the flagellar 

 nucleus, but not always easy of detection, lies the basal structure 

 (fig. 15) of the one flagellum, the latter forming the thickened edge of 

 the undulating membrane. The Trypanosomidse are characterized by 

 the possession of eight fibrillse or " myonemes," which run lengthwise 

 of the flattened body, and of which four are arranged on each side. 

 They are embedded in the thickened outer layer of plasma, and, like 

 the basal structure, they are generally difficult of detection. This 



