124 Maciteay Memortat Vouvume. 
towards the genital cloaca, into which it projects. In shape it varies very much in 
the various species, but in all it is wider—sometimes very much wider—at the 
proximal than at the distal end, and it is invariably armed at the extremity (except 
in 7. Lngez) with a number of sharp chitinous spines. The organ is supported in 
the greater part of its length by a firm chitinous piece, which has the form just 
mentioned —tubular, but much wider proximally than distally. Lining this internally 
is a protoplasmic layer, continuous with that of the vesicula seminalis and of 
precisely similar character, though somewhat thicker. Closely investing the 
chitinous piece externally is a layer of muscular fibres, consisting of two strata, an 
external longitudinal and an internal circular, continuous with the muscular investment 
of the vesicula seminalis and ejaculatory sac. A short terminal part of the cirrus 
differs from the rest of the organ in having a flexible wall, so that it can be 
invaginated and evaginated ; this may be termed the introvert of the cirrus. This is 
continuous with the wall of the cirrus sac; internally it bears a number of pointed 
chitinous hooks or spines, the size, form and arrangement of which vary with the 
species. In certain of the species there is internal to those a single large median 
spine, perforated at its extremity (7. Dendyz, Pl. xu. figs. 7 and 11), or a group of large, 
solid, curved and pointed spines (7. guadrvicornis, Pl. xu. fig. 10). These are terminal 
when the cirrus is protruded ; and while the smaller spines would appear to have the 
function of fixing the end of the evaginated cirrus during copulation, the larger spines 
seem adapted to effect perforation, and perhaps enable the cirrus to be used as a 
weapon. 
Connected with the male reproductive apparatus are a number of glands (PI. xiv. 
fig. 1, and Pl. xv. fig. 1, Av.), the secretion of which contains minute spherical, highly- 
refracting particles, about ‘0014 mm. in diameter in 7. fasczata, of a light yellow colour, 
each enclosed in a spherule of clear uncolourable matter. The cells secreting these 
are closely associated with the tentacular and acetabular glands, but are readily 
distinguishable from them, not only by the nature of the secretion, but also by the 
fact that several cells always completely coalesce to form a pluricellular gland with a 
single duct. They are mainly to be found in two groups on each side—one situated 
between the two testes, the other behind the posterior testis ; but they extend as far 
forwards as the excretory vesicle. These glands (Pl. xu. fig. 4) are usually about +25 
to 3 mm. in long diameter in 7. /fasctata, each consisting of several cells, the 
boundaries of which have completely disappeared ; the nuclei are about ‘014 mm. in 
diameter and are similar in character to those of the integumentary glands, but 
usually somewhat smaller and with a thinner nuclear membrane. The ducts (PI. xu. 
figs. 5 and 6) have very thin transparent walls, and can only be traced by the granules 
which they contain; they frequently branch and anastomose. Two main strands of these 
ducts—an anterior and a posterior—unite on each side near the point where the vas 
