306 MR WALTER E. OOLLINGE ON THE 



sharp bend, gives place to a somewhat conical head. The whole of the distal end is 

 -covered with connective tissue, so that at first sight it has the appearance shown in 

 fig. 37 (PI. III.). When, however, this is dissected away, the S -shaped bend is seen, the 

 tube becoming gradually larger as it nears the point where the retractor muscle is 

 inserted (PI. III. fig. 38). The external wall exhibits a series of ring-like constrictions ; 

 one of these immediately beyond the retractor muscle is much deeper and sharply divides 

 the "head" into two parts, viz., that already described and the conical portion beyond, 

 which has similar constrictions. This gradually tapers off into the vas deferens (PI. III. 

 fig. 37). The vagina is a long, wide tube, having an opening on its dorsal wall for the 

 small, twisted receptaculum seminis, and a larger opening at its posterior end for the 

 small globular free-oviduct. The first portion of the common duct is sharply coiled upon 

 itself. The dart-gland (PI. III. fig. 37, d.gl.) when viewed externally exhibits a globose 

 distal portion, to which a small retractor muscle is attached, a middle tube-like portion, 

 forming the bend, and a dart-sac, the proximal portion. Three specimens were examined. 

 In the first the dart was immature, and had the peculiar bent form shown in fig. 40 

 (PI. III.). In the second specimen this was in much the same condition. In the third, 

 however, a well-formed dart was present, measuring 4 millim. in length. The dart is 

 situated at the posterior end of the proximal sac-like portion. Externally the dart is 

 covered by a calcareous sheath, which has a small, lateralty placed, oval-shaped aperture. 

 The head is not differentiated from the body, which is almost straight and about the 

 same thickness throughout (PI. III. figs. 39-42). 



Under a high power of the microscope, the calcareous layer is seen to consist of an 

 outer structureless layer, and an inner one which, when looked at longitudinally, has the 

 appearance of short dark and light bands (PI. III. fig. 41). This inner layer is more 

 conspicuous in the region of the head than elsewhere. The basal end or annulus 

 (PL III. fig. 43) fits into a groove ; and so far as I could make out the structure, which 

 proved very difficult, the internal cavity of the dart is continuous with that of the 

 expanded distal portion of the dart-gland (PL III. fig. 44). 



The dart-gland consists of a thin external sheath of connective tissue, within which is 

 a longitudinal muscular layer, and then a layer of circular muscle fibres with a few 

 radial fibres intermixed, some of these latter extending as far as, and into, the longitudinal 

 layer. The central cavity is bounded by an epithelial lining (PL III. figs. 45 and 47). 

 Longitudinal and transverse sections were made of both the proximal and distal 

 portions. The former has a glandular lining, and when looked at in surface view, the 

 wall has the appearance of being studded with a series of bluntly pointed papillae 

 (PL III. fig. 49). In longitudinal section these are seen to consist of an outer epithelial 

 layer of cuboid cells, and an inner layer of almost circular cells (PL III. figs. 46 and 48). 

 In the distal portion the epithelial lining consists of columnar cells, and the cavity 

 contains a larger series of exceedingly minute particles (calcareous ?) imbedded in a 

 jelly-like matrix. Sections cut by a freezing microtome were stained in an aqueous 

 solution of magenta, but the matrix remained unstained. Others were treated with 



