G. H. F. Nuttall 
817 
to ixndergo further development in ticks. That such a development 
occurs still remains to be determined although Gonder believes that 
he has partially traced it. 
Remarks upon some other Parasites which appear relaied to 
the foregoing. 
In the foregoing instances we have dealt mainly with thi’ee distinct 
forms of intracorpuscular parasites whose mode of transmission, through 
the agency of ticks, has been demonstrated repeatedly by experiments 
conducted either upon cattle, horses, sheep or dogs. All of these parasites 
hatVe until recently been grouped in the one genus together with certain 
others to which I shall refer more briefly. It has long been evident to 
me that the genus Piroplasma, or Babesia, was being regarded as a 
“hold-all” for parasites of very varied character, and it appears necessary 
to separate them more clearly. Dismissing, then, the three genera I 
have dealt with, viz. Piroplasma, Nuttallia and Theileria, we may 
consider the following: 
“Piroplasma mutans’' Theiler, 1907. 
This parasite occurs in cattle in South Africa and Madagascar; it is 
very minute, resembles Theileria, parva microscopically but for the 
absence of Koch’s blue bodies, and is likewise transmitted by ticks. 
Contrary to Theileria, the parasite is, however, readily transmitted from 
animal to animal by blood inoculation, and is practically harmless in 
respect to pathogenic effects. The parasite is conveyed by Rhipicephalus 
simus, R. evertsi, and, rarely, by R. appendiculatiis. When animals are 
inoculated, a long period of incubation (60-115 <lays) elapses before the 
parasites appear in the blood. These data regarding P. mutans are 
based upon the confused accounts given by Theiler and a few statements 
made by Gonder. I have only studied the parasite in a few stained 
blood-films. It is clear that the parasite requii’es to be adequately studied 
before its position can be determined. 
I would refer briefly, moreover, to the following parasites which have 
been observed in different animals but regarding which we require more 
information : 
Rossiella rossi (Nuttall, 1910), found in the jackal (Canis adustus) in 
British East Africa. The parasite was referred provisionally by me to 
the genus Piroplasma, but subsequently to a separate genus (1912). 
