8 The Philippine Journal of Science wis 



as many zygotes per infected mid-gut and a larger percentage 

 of sporozoites than type indefinitus. The only sporozoites found 

 in indefinitus occurred in the mid-gut and were apparently 

 degenerate. 



* A curious difference was observed in the tendency to develop- 

 ment of ova in the two types. In 3 out of 5 cages and in 39.5 per 

 cent of the total number dissected type Giles showed ova well 

 advanced in development, often as early as the sixth day after 

 feeding, while well-developed ova never appeared in type inde- 

 finitus. In 4, at least, of the 5 pairs males were included with 

 the females in cages. 



Some further observations on these two types and on other 

 types of "rossi will be made in connection with certain tables and 

 in the summary at the close of this paper. From the compara- 

 tive observations on the two types there seems to be substantial 

 evidence for regarding them as distinct forms, biologically and 

 morphologically as well, even though they may not be distinguish- 

 able in the adult stage. Further the question may be raised 

 whether type Giles of Malaya may not be a different form from 

 A. rossi Giles of India. In view of the great variability of the 

 Malayan type, its restricted breeding places, and its suscepti- 

 bility to infection with malarial parasites, it may be at least a 

 biological variant, its characteristics dependent in some measure 

 on its topographical environment. 



In Table II are summarized the laboratory experiments on 

 infection with malarial parasites of various species of Malayan 

 Anopheles. Only controlled lots are included in this table, that 

 is, lots in which at least one insect of some species became in- 

 fected at a feeding. In other words, one or more of the gamete 

 carriers used had viable gametes at the time the feeding was 

 done. In regard to the species included, A. ludlowi is the com- 

 mon brackish-water species of Malaya, having a larva like that 

 of type Giles and an adult resembling A. rossi, but with distinctly 

 speckled legs. In the specimens I have observed the length of 

 the first black palpal band is similar to that of the broader 

 banded specimens of type Giles as described above, but appar- 

 ently h'.dloioi varies less than type Giles in this respect. Ano- 

 pheles ludlowi of Malaya seems to be usually a brackish-water 

 type, though I took some specimens in a large cement-lined 

 reservoir on Kuala Selangor Hill, far above high tide, though 

 near the sea. Whether the Malayan ludlowi is identical with the 

 form described bv Ludlow from fresh water in the Philippines, 



