A Description of the Thread-worm, Filaria immitis. 163 



former occasion mistaken by me for diverticula, or smaller delicate 

 ovarian tubes, from the main uterine canal.* 



Mature Male Worm. — Like that of the female, the body is 

 long, cylindrical, thread-like, straight from the head to within two 

 inches of tail, which is spirally arranged in gradually-decreasing 

 circles terminating in a sharpish free point (Plate XXXI., Fig. 11). 

 Average length of body, 7 inches ; thickness, ^^ inch ; somewhat 

 thinner towards the head than the centre of the body, but markedly 

 thinning off towards tail. The firmer, thinner, whipcord-like aspect 

 of the body and spiral tail, easily, to the unaided eye, distinguishes 

 the male from the female ; the former being to the latter in relative 

 frequency as 1 to 8. The " tube charnu," ahmentary system, and 

 water vascular canals present no deviation from the description of 

 the same in the female worm; it is only when we come to the 

 generative system and the organ for the transfer of the sperm fluid 

 to the germ-containing canal that a divergence becomes necessary. 

 Commencing with the sperm-producing tract, it was found to con- 

 sist of a membranous tube originating in a blind but somewhat 

 pointed extremity about ^ inch from the head ; passing up for a 

 short distance it was reflected on itself (Plate XXXII., Fig. 13, c), 

 and thence traversed the entire length of the worm's body, lying 

 either parallel to or encircling the alimentary canal, from which it 

 would with facility be distinguished by the diminished calibre of the 

 latter (one-half that of the spermatic canal) and the light-refracting 

 quality of the oily contents, ultimately terminating in a vas deferens 

 at the base of the spiculum. The wall of the sperm canal consisted 

 of exactly the same delicate striated and corpuscular membrane 

 forming the uterine wall, the contents only differing. Towards the 

 upper ctecal end of the tube there was a strongly-defined minute 

 epithelium-like layer extending over the entire inner surface, the 

 elements being somewhat larger than, but in character similar to, 

 the free masses lying in innumerable quantities throughout the 

 entire sperm canal. These masses generally had oval club-heads, 

 terminating in the opposite direction in a shm pointed tail (Plate 

 XXXI., Fig. 12) ; their aspect was that of minute, oval, caudated 

 epithelium ; they were strongly nucleated, occasionally tailless, but 

 more frequently than that having two tails opposite the one to the 

 other. Their average size was -xiiro inch in length x ijoVo inch 

 in breadth, yet it was not difficult to find others of half these dimen- 

 sions ; and it will be remembered that these spermatozooids were 

 found also in the uterine canal, both free, and attached to the germ 

 masses. It is apparent that the sexual particles in both male and 

 female were nucleated masses of protoplasm thrown off" from a germ- 

 producing basement tubal membrane, and not inclosed in a capsule 

 or cell- wall as in most of the higher organisms. 



* 'Laucet; March 8, 1873. 



