22 Trypanommes 
notoriously resistant to them, and there are but very few instances recorded 
of successful infection, in a rat or rabbit, and no investigator seems to 
have been able to maintain a laboratory strain for any length of time. 
These trypanosomes, therefore, show a remarkable difference, biologically, 
from the parasite of Algerian or African Dourine, which is said to be 
observable in the general circulation of infected horses, and has been 
transmitted to and canned along in dogs, rabbits, rats, mice, etc. without 
difficulty, becoming exceedingly virulent for laboratory animals. 
Trypanosoma leporis-sylvaticus n. sp. Watson. 
(PI. I. fig. 1.) 
Found in the “cotton-tail bush rabbit,” Lepus sylvaticus, Leth¬ 
bridge, Alberta, Nov. 17, 1906. (Watson.) 
This trypanosome has been observed in about 30 per cent, of rabbits 
shot or trapped at the Lethbridge Experimental Station, 1906-1911. 
Blood infection may be noted at any season of the year but the parasites 
are present in greater numbers and in a greater percentage of animals 
during the late fall and early winter months than at any other time. 
They usually disappear from the'blood of rabbits held in captivity after 
a few days, but occasionally persist for a month or longer period. 
The trypanosome is 26'7 y in average length; it differs from the 
well-known lewisi type in being more slender and elongated, in having 
a more pronounced undulating membrane, a more centrally situated 
trophonucleus, and a larger and more rounded kinetonucleus. 
This trypanosome is apparently non-pathogenic for native and 
domesticated rabbits, mice, and pigeons. (Watson.) 
Trypanosoma peromysci n. sp. Watson. 
(PI. 1. figs. 2, 3.) 
Found in northern deer-mice, Peromyscus maniculatiis, P. nebracensis, 
and other species, Lethbridge, Alberta, Dec. 1906. (Watson.) 
About 20 per cent, of these mice are found infected. The seasonal 
prevalence is similar to that of the rabbit trypanosome. The parasites 
disappear from the blood of mice held in captivity usually on the second 
or third day and have never been seen after a period of seven days. 
The average length of the trypanosome is 28 y. The trophonucleus 
