12S Vniix rsity of California Publications in Zoology, I V(IL - i; 



"tadpole forms" were considered to represent another type, the 

 fact that they divide being regarded as an evidence of maturity. 



Since the discovery of this parasite in the horses of Sene- 

 gambia, numerous other investigators have found various 

 species of animals infected with it, and extended the range of 

 its occurrence across Africa. Two other species of t rypanosomes. 

 T. minion and T. [xcauili, closely resemble <liin<>ri>lii>ii in ap- 

 pearance, and it is possible that the three have been confused. 

 Hut even making- allowance for this possibility, its geographical 

 range is not any the less extensive, and it may be found in most 

 species of domestic animals. Horses are the most susceptible, 

 but cattle, sheep, and even dogs, are all liable to natural 

 infection. 



The investigations of Roubaud (1908) have shown that 

 dimorphon is transmitted from one animal to another by Glos- 

 sina palpalis, but whether the transmission is merely by mechan- 

 ical inoculation, or only after a sexual cycle has taken place in 

 I he intermediate host, is not as yet determined. Roidjaud's 

 theory that the trypanosomes merely undergo a culture in the 

 proboscis of the fly is not in accordance with the observations 

 mii other species, by Prowazek I 1905), Minchin 1 1908), and other 

 investigators. Moreover, the morphological characters and life 

 history of the trypanosome, when in the vertebrate host, are 

 strongly in favor of the existence of a sexual cycle within an 

 intermediate host. 



In the following descriptions the flagellate extremity is re- 

 garded as anterior, for it seems probable from a consideration of 

 the developmental stages of trypanosomes that they are derived 

 from Herpetomonas-like ancestors in which the flagellum is 

 anterior. The two nuclei are referred to respectively as 

 trophonueleus and kinetonucleus ; the mode of division of the 

 latter seems to be sufficient evidence for regarding it as a nucleus 

 and not an extranuclear centrosome. 



TECHNIQUE. 



For the examination of the living parasite a drop of infected 

 blood is placed on a slide and immediately covered with a cover- 

 slip, the edges of which are then tightly waxed down in order 



