A Description of the Thread-worm, Filar ia immiiis. 161 



body was seen to merge into its inner surface, while the longitudinal, 

 and possibly the circular, muscular fibres of the body curved in with 

 the canal, and were continuous with its outer layer. The vagina 

 (Plate XXX., Fig. l,d; Plate XXXI. , Fig. 4) consisted of two 

 clearly-defined muscular layers encircling a narrow canal — a strong 

 outer longitudinal layer continuous with that of the body, a strong 

 inner circular layer stopping short within the vulva, and at the 

 bulbous expansion of the canal, which was observed to be occupied 

 in more than one instance with free embryos (Plate XXXI., Fig. 4). 

 The vagina was rather more than 2^0 inch in thickness, and about 

 ■^ inch in length, terminating internally in two uterine canals, which, 

 after pursuing an individual course for about f inch, merged into a 

 single membranous tube ^V iiich in diameter, traceable, curved 

 around the ahmentary canal and doubled back upon itself, through- 

 out the body of the worm to within 3 inches of the tail end, where 

 it was continuous with the ovarian tubes. The uterine canal, more 

 than four times the diameter of the vaginal, was seen to have its 

 wall made up of a delicate transparent fibrous texture, marked by 

 regular longitudinal lines and faintly oblique or circular ones, and 

 dotted over with so-called calcareous corpuscles (Plate XXXI., 

 Fig. 5). Folds of the delicate wall were numerous, indicating a 

 greatly increased capacity of the tube when required, and fine bands 

 of tissue passed from the outer surface of the wall to the inner surface 

 of the body parietes, thus retaining the canal iyi situ. The con- 

 tinuity of the uterine canal with an ovarian tube is shown in 

 Plate XXXI,, Fig. 7, the former merging into the latter Hke the 

 body of a wine-glass into its stem. The mode in which, however, 

 all the ovarian tubes are connected with the common uterine cloaca 

 is not so apparent. At 4 inches from the tail end of the worm two 

 tubes are to be noted, one, small — intestine; one, large — uterus. 

 At 3 inches there are four ; one intestine, three germ-bearing ; all 

 about the same size. Within this distance and the inferior end of 

 the worm, the caecal termination of the intestine can be observed, 

 and three loops of ovarian tubes. I could not discern the coales- 

 cence of the ovarian tubes with each other, yet from the clear 

 merging of the uterine canal into one tube, I am led to infer that 

 the loops discharge their products into the latter, and hence into 

 the common germ-accumulating canal. The structure of the ovarian 

 walls was similar to that of the uterine sac. The contents of the 

 germ-bearing system varied accordingly to proximity, or otherwise, 

 to the vaginal discharging canal. Commencing with the ovarian 

 tubes, these were seen to be lined throughout with a well-defined 

 layer of epithelium-like cells (Plate XXXI., Fig. 7, a), represented 

 detached and further magnified in Plate XXXI., Fig. 8, a. These 

 masses of protoplasm were irregular in shape, but not uncommonly 

 assumed an ovoidal form somewhat flattened and drawn out at each 



