﻿OBSERVATIONS UPON FILARIA PHILIPPINENSIS. 9 



developed, the oesophagus straight and broad, the intestine narrower and 

 much coiled, particularly at a point corresponding in situation to that of 

 the spiral viseus in the blood embryo. The anus is a slit, directed from 

 within outward and backward (see fig. 17) ; the intestine, apparently, 

 does not terminate at the anus but continues to the end of the body. The 

 tail is tipped with three well-defined papilla?; this number is probably 

 constant, although only two are usually visible in profile. 



By the eleventh or twelfth day some of the filariae may be found in 

 the mosquito's head, by the fourteenth or fifteenth they are encountered 

 in the labium, having completed their development in the insect, so 

 far as we have been able to observe. At this stage the filariae are found 

 within the labium, the fleshy underlip of the insect, where they lie side 

 by side, with their heads directed toward the labella. We have observed 

 as many as foirr within the labium, and it is probable that as a rule they 

 occur in this situation in pairs. (See figs. 13, 14, 15, and 16.) 



As our work has been clone by teasing preparations and not by section- 

 ing, we are unable to state exactly where the filariae lie in the head or 

 how they get into the labium. However, the fact that they do reach 

 that situation is beautifully illustrated in the photomicrographs, which 

 show a fragment of the labium with the tails of the filariae protruding 

 from the proximal end. This preparation was made on the sixteenth 

 day after the mosquito had bitten the filariasis patient. 



The worm, at this stage, has diminished markedly in breadth, the average meas- 

 urement for this dimension being not more than 0.02 millimeter, while individuals 

 have been measured in which it was only 0.015 millimeter. The former figure, 

 however, applies in most instances. The length varies greatly and we have 

 measured specimens which range from 1.236 to 2.20 millimeters. We can say 

 from our observations that the worm when found in the mosquito's labium may 

 average 1.8 millimeters in length, but that others in the same situation and in the 

 same mosquito, actively motile and apparently ready to pass to another host, may 

 be as short as 1.24 or 1.27 millimeters. Two worms taken from the mosquito's 

 head upon the eleventh day gave 1.496 and 1.630 millimeters, respectively, and this 

 variation in length is noticed in individual worms after the very earliest stages in 

 the mosquito. We have thought that the long and short groups may represent the 

 sexes, but have no other evidence to offer in support of such a supposition. (See 

 figs. 10, 11, 24, and 25.) 



At this stage of development the alimentary tract is well defined and 

 extends from the mouth to the anus, which is well marked ; it possesses 

 some strength, as is shown in fig. 9, which represents a worm broken 

 by the attempts made to dissect it from the labium. Here the fragments 

 are held together by the intact cellular tube forming the intestinal canal. 

 The anus is well developed and is easily seen, presenting the same 

 appearance as it does at the eleventh day of development. 



Another point easily determined at this time is that the post-anal 

 papilla? are three in number. Annett, Button, and Elliot state that 



