48 
Piroplasma canis etc. 
adult ticks in the act of oviposition suggesting penetration of the ova 
after these have been laid. In Piroplasma canis at any rate the 
penetration of the ova whilst still within the ovary can be demonstrated. 
The outline of development indicated above enables one for the first 
time to form any conception of the reasons why in some cases transmission 
is hereditary and in others passed from stage to stage, and why in some 
cases hereditary transmission is effective in the larval stage whilst in 
other cases it occurs only at a later ecdysis. 
Both in the haemogregarine and in Piroplasma there is some reason 
to believe that the parasite goes through one and the same cycle without 
reference to the particular stage of growth that the tick has r-eached. 
One can see how details in the life history of particular species of tick, 
or even different rates of development of the parasite, might bring 
about great differences in the transmission of infection without any 
great modification in the actual cycle of parasitic development. 
REFERENCES. 
(1) Christophers, S. R. Haemogregarina gerbilli. Sci. Mem. Officers Med. and 
San. Depart. Govert. India. Xew series No. 18. 
(2) Christophers, S. R. The sexual Cycle of Leucocytozoon canis in the tick. 
Ibid. No. 28, 1907. 
(3) Balfour, A. Second Report of the Wellcome Research Laboratones, Depart. 
of Education, Sudan Govt. 1906. 
(4) Miller, W. W. Hepatozoon periiiciosum. Treasury Depart. Public Health 
and Marine Hospital Service of the United States Hygiene Laboratory 
Bulletin, No. 46. 
(5) Wenyon, C. M. Oriental Sore in Bagdad, together with observations on a 
Gregarine in Stegomyia fasciata, the Haemogregarine of dogs and the 
Flagellates of House Flies. Parasitology, Vol. iv, No. 3. Oct. 1911. 
(6) Koch, R. Beitrage zur Entwicklungsgeschichte der Piroplasmen. Zeitschr. 
f. Hygiene u. Infehtionshr. Vol. Liv. 1906. 
(7) Christophers, S. R. Piroplasma canis and its life cycle in the tick. Sci. 
Mem. by Off. of the Med. and San. Depart, of the Government of India. 
No. 29. 
(8) Marzinowski and Bielitzer. Piroplasmose des Pferdes in Russland und die 
Rolle der Zecke Dermacentor reticulodus bei ihrer Verbreitung. Zeitschr. f. 
Hygiene u. InfektionsJcr. Vol. lxiii. 1909. 
(9) Dschunkowski u. Luhs. Entwicklungsformen von Piroplasmen in Zeckeu. 
9. Internat. Vet. Kongr. Haag. 1909. Ref. Bull. Inst. Past. Vol. viii, 
p. 452. 1910. 
(10) Nuttall and Graham-Smith. The Development of Piroplasma canis in 
cultm’e. Parasitology, Vol. i. No. 3. Oct. 1908. 
