28 The Philippine Journal of Science ms 



In the varieties of rossi, especially, the proportion of these 

 abnormal oocysts is large, even in cases dissected sixteen or 

 more days after feeding. Even if we do not regard these oocysts 

 as degenerate, but merely much retarded in growth, the occur- 

 rence of so large a proportion of them must affect the species 

 as a carrier of malaria, since the delay in formation of sporo- 

 zoites would materially decrease the proportion of infected mos- 

 quitoes surviving to transmit infection. In all varieties of rossi, 

 34 mosquitoes exhibiting only abnormal oocysts were found, 

 while cases that showed sporozoites in either gut or salivary 

 glands totaled only 33. The temperature prevailing during these 

 experiments was high and so nearly uniform that differences 

 in the rate of development of malarial parasites could be hardly 

 ascribed to variations in temperature. 



MOSQUITOES INFECTED IN NATURE 



In Table XV are summarized by species the results of dissec- 

 tions of mosquitoes caught in the adult stage. None of these 

 were subsequently exposed to a carrier except in the case of a 

 lot of 14 umbrosus, of which three had sporozoites in the sali- 

 vary glands. These fourteen were caught in the hospital of a 

 certain rubber estate and later exposed to a carrier. They were 

 dissected five to eight days after feeding, and three had sporo- 

 zoites- in the salivary glands. Since it is highly improbable that 

 sporozoites could be formed in the salivary glands within eight 

 days, it seems fair to reckon these three with the naturally in- 

 fected lot. Other specimens of umbrosus caught at the same 

 time and place and not subsequently exposed to a carrier showed 

 sporozoites in the salivary glands. 



It has seemed worth while in the table to classify the dissec- 

 tions of the different species according to the locality in which 

 the mosquitoes were taken. In all cases the mosquitoes were 

 caught in places where gamete carriers might be expected, but 

 the degree of probability of infection varied greatly in the dif- 

 ferent localities. The probability was the least in "houses near 

 the coast," although two positive umbrosus were found there at 

 different times (at Port Swettenham). The "plantation coolie 

 lines" were in all cases highly infected with malaria. In "hos- 

 pitals" most of the collections were made in the malaria ward of 

 a large hospital, where many cases of malaria were admitted, 

 or in the hospital of a highly infected plantation. 



