BY T. HARVEY JOHNSTON. 401 



Seligm.). However, this is not commonly the case. Other 

 genera have been proposed, whose characters are based mainly 

 on the relative sizes of the host-cell and the parasite; l)ut I 

 intend to follow Sambon in regarding the family as consisting of 

 a single genus, Ihemogregarina Danilewsky (Laveran emend.). 



Sambon(l) states that these animals pass through a cycle in 

 their life-history, which in many ways resembles that described 

 for malaria ^^v^^\t&s,{Plasmodium spp.V Keproduction may be 

 brought about by sporogony or by schizogony, i.e., sexually or 

 asexually, respectively. In the asexual stage, the cycle is passed 

 through in the blood of a vertebrate (schizogony); whilst the 

 sporogonic, or sexual phase, occurs in the body of some blood- 

 sucking ectozoon such as a tick or louse, in the case of land- 

 animals; or a leech, in the case of aquatic hosts. Thus the final 

 or definitive host {i.e., the host in which the parasites become 

 sexually mature) is an ectoparasite, whilst the intermediate host 

 is one of the higher animals. He also states, further, that 

 in the intermediate host, two different adult organisms may 

 be produced, viz., the schizont and the sporont. The schizont is 

 known to break up into a number of merozoites which become 

 liberated into the blood-plasma, and may infect blood-corpuscles 

 of the same host. The sporont is destined for removal by the 

 definitive host, on reaching whose gut it gives rise to micro- and 

 macrogametocytes. These conjugate to become ookinites capable 

 of again entering and reinfecting the vertebrate when occasion 

 offers, i.e., they may become extruded with the saliva of the 

 ectoparasite, whilst it is sucking its host's blood. I have not 

 seen schizonts in any of the films examined. Perhaps their 

 appearance is periodic. 



So far very few Haemogregarines are known from Australia. 

 They are 



(a) Hcemogregarina shattocki Sambon and SeligmanD.(l,2) from 

 an Australian diamond-snake, Python sjnlotes Lacep. 



(b) //. dasyuri Welsh and Barling,(3) from the " Native Cat," 

 Dasyurus viverrinus Shaw (New South Wales). 



41 



