334 PROCEEDINGS OF SECTION D. 



Female. — The ovaries are double and lead straight into the 

 long and slightly coiled double uterus. The wall of the uterus 

 (fig. 32), when undistended, consists of distinctly nucleated and 

 granular cells surrounded by a very thin fibrous layer. When dis- 

 tended the wall appears as a very thin fibrous one in which nuclei 

 are apparent, cell divisions being apparently lost. The two uteri 

 unite without much change of structure to form a common uterus 

 of remarkably varying length. This in turn opens to the exterior 

 at the vulva by a short muscular vagina. The vagina is seen in 

 specimen C, which was the only infertile one of these six, to be 

 0.414 mm. long, having close to the vulva an even more muscular 

 swelling {see fig. 6). The single uterus, non-muscular or only 

 sHghtly so, passes back for a distance of 1.38 mm. before dividing 

 into the two uteri corresponding to the two much coiled ovaries. 

 As remarked above, this specimen contains no fertilised eggs or 

 larvae. 



In other cases the total length of the vagina and common 

 uterus varies from 1.656 mm. to 5.10 mm., in each case being 

 crowded with larvae, as is also one or both halves of the bifurcated 

 uterus. There is, so far as our specimens show, no relationship 

 between the position of the vulva relative to the head and the 

 length of the common uterus. 



Development. 



By counting the average number of larvae in a transverse 

 section of known thickness, and calculating the egg-bearing area 

 of the shortest and longest worms measured, we have estimated 

 the number of fertilised eggs and larvae present in the worm at any 

 one time as certainly not less than 400,000 in the shortest to 

 2,000,000 in the longest. In the case of those nodules in which the 

 male worm is present with the female the possibility or even prob- 

 ability of nearly continuous, or at least repeated fertilisation en- 

 ormously increases the reproductive capacity of these worms, a 

 fact which undoubtedly points to the life-history being a very 

 difficult one, with every likelihood of non-completion. As re 

 marked above, very few infertile nodules have been found, and even 

 where fertile very often no sign of the presence or even past presence 

 of a male could be found. 



The unsegmented fertilised ovum {see fig. 13) is 0.017 mm. by 

 0.009 mm., the nucleus being large, round, and finely granular. 

 Segmentation proceeds very rapidly, so that in good smears from 

 the cut surface of a fertile nodule the full process of segmentation 

 can be traced. 



The first result of segmentation is very commonly met with in 

 such a smear, and this two-celled stage shows very considerable 

 variation in size, even more than shown in the figures {see figs. 14 

 and 14a), namely, from 0.019 mm. by 0.009 mm. to 0.02 mm. by 

 0.017 mm. Thence division proceeds more or less regularly, as 

 shown in figs. 15-18 : four, five, six, seven, ten, fourteen, sixteen. 



