PART III.] Detailed Descriptive Anatomy of the Parasite. 545 



power has been used to make out the structures than the extent of amplification 

 stated opposite each figure would imply. To have drawn the figures to scale, as 

 observed under higher powers, would have added greatly to the difficulties of repro- 

 ducing them without adding materially to their value. Figure 16, Plate XL, represents 

 the anterior portion of the mature parasite ; the mouth with its six, indistinctly marked, 

 " lips ; " the chitinous pharynx, and the upper portion of its muscular oesophagus : 

 whilst the adjoining Fig. (17) gives the appearance of the mouth and entrance to 

 the pharynx as seen from the front. Figure 18 represents the ventral aspect of the 

 tail of the male with its two dissimilar spicules and four pre-anal papillae — characters 

 which, when taken in conjunction with the arrangement of the muscular tissues of 

 the body, form the distinctive features of the genus Filaria (Schneider). There 

 are also two post-anal papillae, placed transversely to the body of the worm ; so that 

 in all there are twelve papillae, terminating on the inner surface of the alae which 

 form the boat-shaped cavity on the ventral aspect of the coiled tail of the male. 



The mode of formation of this cavity will be more readily comprehended by a 

 reference to Fig. 1 9, which represents a dissection of the tail of the male as seen from 

 the side (magnified 30 diameters). It will be observed that the cuticular and muscular 

 sheaths of the worm have been slit up, and the two retractor muscles (e e) continuous 

 with the sheath (/ ) of the larger spiculum, are seen to arise from either side of the 

 left lateral band. (The well-marked curvature of the tail in the male, so common among 

 the Filaridce, is, in this case certainly, due in a great measure to the strength and 

 elasticity of the larger spiculum ; when this is extracted the curvature loses its firm- 

 ness.) The alimentary tube (a) is seen to run parallel with the spermatic tube (6 c), 

 a sphincterlike constriction occurring on the course of the latter, separating the " vas 

 deferens " (b) from the " testis " (c). The " testis " consists of a tube extending upwards 

 in a serpentine manner until the junction of the upper with the middle third of the 

 body and terminating caecally as shown at (d). Figure 20 represents the molecular 

 and cellular contents of this tube. 



The head of the female worm (Fig. 21a,) does not differ from the head of the male, 

 except that it is somewhat larger. The specimen delineated had been immersed in spirit, 

 which had separated the chitinous cuticle from the other tissues ; so that the continuation 

 of the former with the pharynx has been made very evident, the pharyngeal membrane 

 being merely a reflection inwards of the skin ; a similar reflection takes place at the 

 other end of the alimentary canal. The course and texture of the oesophagus and 

 intestinal canal are the same as in the male, and do not differ from such structures 

 in the Filaridce generally. 



The vagina (Fig. 21 6) terminates about |^th of an inch below the oral extremity 

 generally a little above the junction of the oesophagus with the intestine, as represented 

 in the plate. It is a well-developed muscular tube, composed of longitudinal and trans- 

 verse fibres, and the channel is occupied by a row of ova lying two or three abreast. 

 It is about |th of an inch in length, is curved upon itself about the middle and 



37 



