381 DR. P. MANSON ON THE METAMORPHOSIS OF 



Tliey showed no double outline, transverse striatiou, or sheath ; hut oval pouting and some 

 general body-movement still persisted. As yet tail-differentiation was not discernible. Beyond 

 a few undefined specks the body was homogeneous. Perhaps the mouth possessed four lips. 

 Slide prepared with sulphate-of-soda solution gradually washed away with pure water. 

 Fig. 4. From the thorax 25 hours after feeding. The abdomen of the mosquito still contained fluid, or 

 semifluid blood, about two thirds full. In this eight passive Filarice were found ; they were 

 granular and evidently dead or dying. Over two dozen Filarice were found in the thorax, most 

 of them active, with differentiation of the tail commencing. That represented measured 



loir A 2Boo • 

 Figs. 5, 6. From the thorax 35 hours after ingestion. The abdomen of the insect was about two thirds filled 



with blood, in which 12 or 13 undefined, granular, dead, and fading Filarice were found. One of 

 them, however, which evidently had been about the periphery of the clot, was well defined, faintly 

 striated, plump, moving freely, and had a tail slightly differentiated. Many were found in the 

 thorax ; all of these were passive and had distinctly differentiated caudal appendages. No 

 organs seen; body-contents granular. The body appears to be expanding, the enlargements 

 being most apparent towards the tail end. One measured xio" x ^oW'j another x4o" x Woo"- 

 One or two exhibited slight movement, cither slow bending and extension, or, at loug intervals, 

 sudden jerking extension. 



Fig. 7. From the thorax, 39 hours. Large number of Filarice in the thorax. For the most the tail was 

 well differentiated. The body of the parasite had become thicker and shorter. In some, on 

 washing away the sulphate of soda solution, a double outline could be made out. Contents 

 cloudy and granular. Jerking movements frequent. A very few of the Filarice were shaped 

 and moved as in mosquitoes examined a short time after feeding ; that is, they were long 

 slender, active, with a tapered tail. Between these and the distinctly tailed animal transition- 

 forms were abundant, so that there could be no doubt about the connexion. Specimen repre- 

 sented measured xis" x or,\ M) ". 



Figs. 8-10. From the thorax of mosquito 46 hours after capture. Many Filarice were found in this 

 insect at different stages of development, from the long, slender, rather active Filaria with but 

 slightly differentiated tail, to the fat tailed sausage-form with granular contents and intermittingly 

 wagging tail. Fig. 10 shows the chitinous integument, dipping into the rudimentary mouth; 

 it is drawn to a larger scale. In one field of the microscope three Filarice lay across each other; 

 one had hardly made any progress in development, another was still slender, but the tail was 

 differentiated, while the third was thick, plump, and sausage-shaped. 



Figs. 11, 12. From the thorax 56 hours after feeding. 



The insect was found dead at 2 p.m., but was seen alive the same morning. Many live 

 Filarice found in this insect, exhibiting the extension of the body and flick of tail movement. 

 Fig. 11 showed some body-extension and a remarkable vibration of the whole of the posterior 

 part of the body. The contents were in marked contrast to those of No. 12, being a structure- 

 less homogeneous matrix interspersed with innumerable, well-defined, shining granules ; it 

 measured X2s" x rnJo''* Fig. 1~ measured X4s'' x x^Su"' ^ possessed no body-movement, but 

 only the tail-flick. Its body was made up of distinct cells ; one minute, glistening, nucleated, 

 cell-like body was a prominent feature at a point where the anus might be. Many more 

 Filarice like these two types in the slide. 



Figs. 13, 14. From the thorax 72 hours after capture. Many Filarice much broader, and somewhat 

 longer, than those from the mosquito of figs. 11, 12, which belonged to the same batch of insects, 

 and examined the day before. The tail was not seen to move, and no movement of body 

 could be detected. Obscure cellular arrangement of the body. In all specimens a crowd of 

 granular matter escaped from the anus. Fig. 14 measured xio" x Too" anteriorly, and - s \- 5 n 



