68 COLLINGE : ON THE ANATOMY OF THE VITRINA IRRADIANS. 



papilla was present, reminding one very much of the condition 

 obtaining in certain Indian species of Ni/tjiria, only there was no 

 trace of the ^^ virtjula amatoria.'' 



Serial sections were made of both the gland and dart-sac, which 

 proved very interesting. Below I give descriptions of the transverse 

 sections. Externally the gland is seen (Fig. lo) to be covered by a 

 thin muscular sheath (vi.s.), beneath which is a thick layer of large, 

 ovoid and circular gland cells ([/I. c), with radiating muscle fibres 

 intervening. In the section from 'which the drawing is made, there 

 are twenty-eight of these bundles of radiating fibres, they do not, 

 however, traverse the whole length of the gland, but in longitudinal 

 median sections are seen to be irregularly arranged at varying inter- 

 vals, somewhat in the same manner as the medullary rays are in the 

 stem of a plant. They extend from the outer side of the lining epi- 

 thelium (1. ep.) up and into the large gland cells. Internal to this 

 glandular tissue are bundles of longitudinal muscles, followed internally 

 by a ring of circular muscle fibres (c. m.f.). The central portion of 

 the gland consists of a loose connective tissue, with small, round cells 

 scattered throughout, bounded on its inner face by the small, cuboid, 

 lining epithelial cells, which arc arranged in a wavy outline and bound 

 a small, central cavity. A somewhat similar structure has been indi- 

 cated by Weigmann'-' in Xesta cinda, Lea, and X. halmahcrica, Strub.* 



A similar section through the dart-sac exhibits the following 

 structure : externally there is a layer of fairly large, cuboid epithelial 

 cells (Fig. ir, e. p.) with muscle fibres and connective tissue below, 

 then a series of small, rounded cells, scattered amongst more con- 

 nective tissue. The dart consists of an external layer of muscle, 

 connective tissue and small cells, followed by a la\er of circular 

 muscle fibres, then a mass of tissue similar to that in the dart-gland, 

 bounded by cuboid e[)ithelial cells^ which enclose a small, central 

 cavity. 



The common duct is folded twice, and the prostatic portion stands 

 out conspicuously. The hermaphrodite duct is closely coiled, and 

 the gland is small and somewhat pyriform (Fig. 2, li. gl.). 



The Free Muscles (PI. vi, fig. 12). — The buccal retractor divides 

 anteriorly into two branches, each of which again divides, the four 

 muscle bands being inserted on the ventral side of the buccal cavity. 

 The oculars are similar on both right and left sides, the inferior and 

 superior being separate for over half the length. From the former a 



9 Abhandl. d. Senckenb. naturf. Gesell., 1S98, T. xxv, fig. 23, T. .\.\vi, fig. 8. 

 * Semper also gives good figures. 



