REPORT ON THE SIPHONOPHOR^. 231 



and subject to many variations. The majority of the bracts have the form of a flat obelisk, 

 or an irregular truncated four-sided pyramid, sometimes more approaching to a regular 

 four-sided prism, at other times to an irregular spheroid. There are intermingled, too, 

 three-sided and five-sided (or even six-sided) truncate pyramids between the prevailing 

 four-sided ones. The four trapezoidal lateral faces are usually of nearly equal size ; the 

 lower or basal terminal face is more or less concave, and about twice as large as the upper 

 or apical face. The edges are slightly convex and armed with a series of cnidocysts, a 

 larger one being prominent from each angle (fig. 10). A single blind bracteal canal (figs. 

 5 and 6, cb) arises from that corner of the basal face which is attached by a short 

 mobile pedicle to the trunk. The canal runs along the middle line of the concave basal 

 face to about its centre, and ends there in a club-shaped blind dilatation. 



Siphons (figs. 5, s, 6, s, 7). — The single polypite of each cormidium is relatively large, 

 very contractile, transparent and colourless, and attached to the trunk by a short pedicle 

 (sp). The entire surface of the siphon is covered with very long vibratile cilia, arising 

 from the exoderm cells (fig. 7). The basigasteris rudimentary. The large stomach (sm) 

 is spindle-shaped, and contains inside four longitudinal rows of prominent hepatic villi, 

 each row composed of half a dozen conical villi (sv). Each villus seems to be a single 

 very much enlarged, glandular entoderm cell, which contains besides the nucleus a large 

 roundish hyaline vesicle, probably a digestive vacuole. Many stomachs were filled with 

 the eaten tentilla of the animal itself. The proboscis (sr) is a long cylindrical tube with 

 a very thick and mobile muscle-wall. It opens at the distal end by a very expansde 

 mouth, the edge of which is armed with thread-cells (fig. 7, so). The mouth may be 

 expanded and attached in the form of a circular or polygonal suctorial disc (fig. 5, ss); 

 this becomes sometimes as large as the entire cormidium. 



Tentacles (PI. XV. figs. 5, t, 6, t, 7, t, 11-13). — The single tentacle, which is attached 

 to the base of each siphon, is very long and bears a series of very numerous tentilla. 

 Each tentillum is composed of a long pedicle (fig. 11, ts), an ovate cnidosac (k), and a 

 thin simple terminal filament (tf). The pedicle is beset with numerous papillate villi 

 (fig. 11, tv). The proximal half of the cnidosac is enclosed by a campanulate and ciliate 

 involucre, whilst its distal half is free and beset with numerous, very large, radially 

 distant cnidocils. The proximal base of the cnidosac contains a vesicular diverticulum of 

 the canal, the middle part a horizontal turning of the spiral cnidoband, beset on both 

 sides with a series of very large ensiform cnidocysts (kg) and above it a red pigment- 

 spot ; the distal end of the cnidosac is filled by globular cnidocysts. Whilst fig. 1 1 

 in PI. XV. exhibits the fully-developed tentillum, two immature stages of its develop- 

 ment are represented in figs. 12 and 13. 



Cystous (figs. 5, y, 8, 9). — The single cyston, which is attached in each cormidium 

 near to the base of the siphon, is about half as large as the latter. It consists of three 

 parts : a short and small pedicle (yp), a large spherical thin-walled bladder, covered with 



