76 J. B. CLELAND AND T. H. JOHNSTON. 



if indeed actually distinguishable, differences in the part 

 of the life cycle examined by us, from other known forms. 

 We have decided, however, to do so tentatively and for the 

 following reasons : — 



1. In mammals, the parasitic haematozoa seem as species 

 to be absolutely confined to one species of host only, or if 

 found in more than one, the species so affected are closely 

 allied members of the same genus if not varieties of each 

 other (e.g. the malarial plasmodia of various races of man, 

 the leucocytozoon of Mus rattus and decumanns). We 

 have supposed that the same is likely to hold good, to some 

 extent at least, amongst the Aves and so, in the present 

 state of knowledge, pending actual experimental inocula- 

 tions into species-hosts of other genera, we have decided 

 to class as distinct the parasites occurring in hosts not 

 belonging to the same or a very closely allied genus. 



2. It will coordinate the results of a complete examin- 

 ation of the avian kingdom for protozoal parasites, if a 

 specific name and a full description is appended to the 

 parasite of any particular species, by which the parasite 

 can be, as it were, labelled and handled. For this reason, 

 as is now the custom, we have applied, as the specific name, 

 the name of the genus to which the host belonged. 



The Halteridia which we have found in Ptilotis chrysops 

 and Philemon comiculatus call for little comment. An 

 interesting form, in which multiple infections of single host- 

 cells occurred with much frequency, was seen in that of 

 Meliomis novce-hollandice. In the Halteridiumof Geocichla 

 lunulata numerous free or nearly free gametocytes were 

 seen and also interesting forms which suggested to us the 

 formation of two separate gametocytes, one at each end, 

 from single halter forms in some cases. 



To the end of the paper, we have appended a short note 

 on the superficial resemblances shewn between the sper- 



