OF FILABIA SANGUINIS HOMINIS. 



309 



microscope, and probably depends on some oily material now 

 collecting in the body of the animal. 



This concludes the first stage of the metamorphosis, and has 

 taken about thirty-six hours to complete. During all this time 

 the original proportions of the animal have been preserved and 

 vigorous movement maintained. Now, however, it enters on a 

 sort of chrysalis condition, during which nearly all movement is 

 suspended, and the outline and dimensions very much altered. 

 Hitherto the body was long and of graceful contour, but now it 

 becomes shorter and broader, the extreme tail alone not partici- 

 pating in the change. The large spots in the body disappear, 

 gradually giving place to what seems to be a fluid holding nume- 

 rous minute particles in suspension. I have once or twice detected 

 to-and-fro movements in these. The tail continues to be flexed 

 and extended vigorously, but only at long intervals, whilst all oral 

 movements cease. By the end of the third day the animal has 

 become much shorter and broader, the small terminal portion of 

 the tail still retaining its original dimensions, and appearing to 

 spring abruptly from the end of the sausage-shaped body. Large 

 cells occupy the previously homogeneous-looking body, and some- 

 times something like a double outline can be traced. Indications 

 of a mouth present themselves ; and if a little pressure is applied 

 to the covering-glass, granular matter and cell-like bodies escape 

 from an orifice placed a little in advance of the tail. The animal 

 now begins to increase in length, and in some specimens to dimi- 

 nish in breadth, the growth seeming to be principally in the oral 

 end of the body. The structure of the mouth is sometimes very 

 evident ; it is four-lipped, the lips being either open or pursed up. 

 From the mouth a delicate line can be distinctly traced, passing 

 through the whole length of the body to the opening already re- 

 ferred to as existing near the caudal extremity. Feeble move- 

 ment may still sometimes be detected in the caudal appendix ; but 

 when the now growing body has attained a certain length the 

 tail gradually disappears. 



After this point, specimens of the Filaria in its third and last 

 stage are difficult to procure. Most mosquitos die about the 

 fourth or fifth day after feeding ; and if their bodies, which fall 

 into the water, are examined, they are soft and sodden and with- 

 out Filarice, these having either decomposed or escaped. Some- 

 times, however, ovulation does not proceed rapidly, and the 

 mosquito survives to the fifth or sixth day ; or perhaps death may 

 not occur, as it usually docs, soon after the eggs ha^ c been laid, 



