298 



H. M. WOODCOCK. 



some ; medium length about 50 ji, breadth 3i — 4^. It is thus readily dis- 

 tinguished by its size from the other Mammalian forms, although it agrees 

 with most of them in being of the typical fusiform shape. It appears to be 

 confined to Bovidse, occurring especially in the Transvaal, and causing the 

 disease of cattle known as " Galziekte " or bile-sickness. Herds of cattle 

 imported from Argentina, Texas, etc., are particularly liable to suffer from 

 it. Theiler, who discovered the parasites, thinks that they are transmitted 

 by a biting fly, Hippobosca rufipes. Another species, H. maculata, 

 recently imported with cavalry from India, may also aid in spreading the 

 disease. T. transvaaliense (fig. 50 c — e) averages about SO /i in length 

 by 4/i in width. From the dimensions given (though not, apparently, from 

 the figures) it would appear to be rather wider than T. theileri. Its 

 distinguishing morphological feature, however, is the position of the kineto- 



PiG. 50. — a and b, T. theileri; c — e, T. transvaaliense. 

 e is a small form dividing, x 1250. (After L. and M.) 



nucleus ; this organella is rod-like and situated in contact with the tropho- 

 nucleus. Correlated with this, the undulating membrane is short and 

 poorly-developed. Moreover, this variety is quite capable of division 

 (fig. 50 d), even in the case of very young individuals (e). Nevertheless, 

 Theiler has recently observed transitional forms, intermediate between T. 

 theileri and T. transvaaliense, with a varying distance between 

 the tropho- and kineto-nucleus. This author has also found that, on 

 inoculating the latter variety into Bovidae, the former (T, theileri) 

 is produced in time as well. These facts would seem to show that the 

 two forms are not really independent and distinct species. 



