﻿8 ASHBTJRN AND CRAIG. 



By the third day, possibly earlier at times, the filarial have left the 

 abdominal cavity and are to be seen among the thoracic muscles of the 

 mosquito, where they show very sluggish motion and are observed to have 

 undergone a very marked change in morphology. 



The length has decreased from 0.32 to 0.21 millimeter; the breadth has 

 increased from 0.0065 to 0.01 millimeter; all parts of the body have 

 participated in the increase in width except the tip of the tail — that is, 

 the part of the tail back of the sudden diminution described in our first 

 paper. This part has not enlarged in size, and, as will be seen, it- 

 disappears at a later period, thus fulfilling the prediction concerning it 

 which we made in our first publication. The posterior V spot is still 

 visible and is manifestly increased in size. The body presents a granular 

 appearance and the central viscus has disappeared. (See figs. 2, 3, 19, 

 and 20.) 



At the end of six days the filaria? are still as short as at three days, 

 but they have undergone a further increase in breadth which at this stage 

 varies from 0.014 millimeter near the anterior end to 0.027 millimeter 

 near the posterior, the average being about 0.02 millimeter. The tip 

 of the tail is still present and still unenlarged and now presents a "pigtail- 

 like" appearance in its attachment to the more bulky body. The latter 

 still has a granular aspect but some cell structure can be made out and 

 the alimentary canal outlined. The posterior V spot, as such, has disap- 

 peared, but its place is occupied by a rudimentary anus. The motion of 

 the worm is still sluggish, being about the same as it is at the third 

 day. (See figs. 4, 5, and 21.) 



On the eighth day we find the filaria increased in length and in breadth ; 

 the "pigtail" portion of the tail in most instances, though not in all, 

 has disappeared; the alimentary canal can be traced the whole length 

 of the worm. The length averages about 0.6 millimeter, the breadth 

 0.035 millimeter; motion is sluggish but the filaria is possibly a little 

 more active than it was at the sixth day. (See fig. 22.) 



From the eighth to the eleventh day the worm undergoes a more rapid 

 development than in any other similar period and at the expiration of 

 this time is found to have attained a length of from 1.2 to 1.6 millimeters 

 and a width varying from 0.04 down to 0.02 millimetel*, the width being- 

 less in the longer worms. (See figs. 6, 7, 8, and 23.) 



Some worms at this time show as complete a development as we have 

 ever seen and apparently have no other change to undergo except the 

 lengthening and narrowing, a change of form rather than of size, neces- 

 sary to enable them to enter the labium. The head is truncated, the 

 mouth a terminal, crater-like, circular opening, forming the base of a 

 conical cavity; no lips are visible. Nothing recognizable as the analogue 

 of the anterior A" spot is distinguishable. The intestinal canal is well 



