Proteosoma to Birds ly the Mosquito. 451 



appearance of their contents, into clear and granular ; the evolution 

 of the latter into the coccidia containing germinal threads can be 

 traced day by day. This differentiation was clearly visible in my series. 



In a minority of the coccidia, and in most infected mosquitoes, 

 when the germinal threads are mature, certain black tubular bodies 

 are to be found in cysts with otherwise clear contents. These black 

 tubular bodies were frequently met with in the series of mosquitoes 

 infected in November and December. Most of these mosquitoes con- 

 tained some coccidia with black tubular spore-like bodies; though 

 in a few insects all the cysts contained germinal threads only. In 

 some cysts the black spores were numerous, and occupied the entire 

 cyst ; in other cysts there were only a few. In most instances germinal 

 threads were not found in the black spore-bearing cysts ; but there 

 were a few such cysts in which it was doubtful whether germinal 

 threads were present or not, or whether the appearance arose from 

 over-lying threads which had escaped from a neighbouring capsule. 



These black spores are very resistant ; I have seen some which had 

 been kept in water for months by Eoss, and -which had undergone no 

 visible change. They withstand irrigation with liquor potassae. 



When the cysts are ruptured the black spores are to be found all 

 over the body of the mosquito, but not included in cells. They do not 

 seem to accumulate in any particular organ. 



The most plausible view of the nature of these black spores seems to 

 be that held by Major Ross, viz., that they are " resting spores," and 

 that through them, by another cycle, the Proteosoma can be propagated 

 in conditions unfavourable for direct propagation by mosquito-insertion 

 into a warm-blooded animal. 



If this be the case, three courses suggest themselves : 



(") From the black spores may arise bodies capable of non-parasitic 

 life (and possibly of reproduction), which at certain stages 

 of their existence, and in certain conditions, on introduction 

 into a warm-blooded host by inhalation, through drinking 

 water, or even by injection by a mosquito or other blood- 

 sucker in transferring them from the medium in which they 

 live, may resume parasitic habits. 



(I) That they may be ingested by mosquito larvse, and in them 

 undergo such development as will result iu the formation of 

 germinal threads in the adult mosquito, which, in turn, may be 

 injected into the appropriate bird. 



(c) That they may, if swallowed or inhaled by an appropriate warm- 

 blooded host, so develop as to reach the circulation and pass 

 into the sporulating phase. 



Such experiments as have been made on this subject are inconclusive ; 

 and it is obvious that until the nature of these "black spores" is 

 VOL. LXIV. 2 M 



