62 PROCEEDINGS OF THE NATIONAL MUSEUM vol.70 



The vagina opens on the ventral side of the cirrus. It communi- 

 cates with a relatively spacious seminal receptacle, which lies on the 

 median side of the inner seminal vesicle. The lining of minute 

 spines, noted in the exterior portion of the vagina of F. falciformiSy 

 was not observed in any of tlie sections of this species. The ovary is 

 tubular, in some cases slightly branching, and lies on the ventral 

 side of the medullary space, near the median line. The vitelline 

 gland is slender and lies ventral to the ovary. As is shown in figure 

 196 its length may be more than three times that of the ovary as 

 seen in transverse sections of the strobile. FigTire 198 is from a 

 camera lucida sketch of the complex of female genital ducts as it 

 appeared in a series of sections of an unripe portion of a strobile, 

 the uterus, only, being diagrammatic. In ripe portions of the stro- 

 bile ova fill practically all of the medullary space. Here and there, 

 however, in the series of sections, there are indications of an earlier 

 tubular stage of development of the uterus, as is shown in the 

 diagram. The ova, as they appear in these sections, have thin shells, 

 and have a maximum diameter of 0.036 mm. 



The thickness of the cuticle as about 0.003, of the subcuticula,, 

 about 0.17. The latter is granular, crossed with fine, radial fibers, 

 and contains large numbers of calcareous bodies; some of these 

 bodies are circular in outline, but most of them are oval, and range 

 from 0.007 to 0.014 in the major diameters. Next within the sub- 

 cuticula there is a layer of longitudinal muscle fibers consisting of a 

 single circle of fascicles. These fascicles are irregularly oval in 

 cross section, the longer diameter radial, and the cross sections ap- 

 proximately 0.052 by 0.024 in the two prinicpal diameters. Within 

 the layer of longitudinal muscles there is an inconspicuous layer of 

 fine granules with a few circular fibers. 



The water vascular system consists of three pairs of prinicpal 

 vessels, which are more or less sinuous; a pair situated at a distance 

 equal to about one-fourth the breadth of the strobile from each 

 lateral margin, and a third pair not far from the median line. These 

 vessels, with the exception of the enlarged median one, are small and 

 of nearly uniform size, about 0.015 in diameter. The walls of these 

 vessels are relatively rather thick. The difference in size between 

 the large vessel of the median pair and that of the other longitudinal 

 excretory vessels is striking. Thus, in a transverse section through 

 a portion of the strobile where the reproductive organs were mature, 

 but no ova had yet appeared, the diameter of the more marginally 

 placed vessels, and the smaller of the median pair, was about 0.015, 

 while that of the median large vessel was 0.08 by 0.15 (fig. 196). 

 In a section made through a portion of the strobile where the 

 medullary space was filled with ova, and no trace of the smaller 



