PLATE V. 



C. gracilis. 



Fio-s. 43—53 (Zeiss, C) are obliquely sagittal sections of the specimen of which reconstructions are shewn 

 in PI. III, figs. 22, 25. The specimen liad a strong lateral flexure towards the right, so that 

 in figs. 50 — 53, the animal is out in two separate pieces. It was abnormal in having a com- 

 munication between the posterior side of the stomach and the intestine. The series starts with 

 fier. 43 which is near the middle line, and proceeds outwards towards the right side of the 

 body. Figs. 46 — 50 represent consecutive sections. 

 Fig. 43, near the median plane, cuts the mouth (w/.), pharynx (//;.) and oesophagus [ocs.) nearly medianly. 



The peritoneum [pt.) is loosely attached to the stomach, and does not enter the interval (probably 



in the main artificial) between the stomach and the intestine. The dorsal part of the collar-cavity 



{b. c?) is that of the left side, with the bases of the last three arms {L. 3 — 5). The stalk, which 



is cut at a bend, shews its anterior nerve-tract (;/. /.) : — g. s., pleurochordal tissue of dorsal 



diverticulum of pharynx, continuous with the left gill-slit. The ovary (oz>. l.) is that of the left 



side. The operculum (op.) is shorter than in the more lateral sections. 

 FÏCT. 44. ƒ., end of the fold of the body-wall, which divides the sections shewn in figs. 50 — 53 into two 



parts; ov.r., median edge of right ovary; pL, pleurochordal tissue continuous with right gill-slit. 

 Fier. 45 passes just to the right of the mouth. The arms of the left side (L. i — j) extend beyond the 



middle line of the coUar to the right side of the animal ; the base of the stalk (st.) is cut, and 



the opening of the second stomach [stom}) from the main stomach: — b.cr, right collar-cavity; 



*./., internal opening of right proboscis-pore ; ■;-., right wall of rectum; ov.v. branch from dorsal 



vessel to left ovary; g. s., wall of gill-slit. 

 Fio-. 46. — The ventral half of the body, which is completely separated from the dorsal half by the fold of 



the body-wall (ƒ) seen in fig. 45, is not represented : — c.c.i., internal opening of right collar-canal; 



cr.s.c, external opening of gill-slit; ovd., left oviduct, from which a discharge of pigment is 



taking place. 

 Fig. 47. — /., proboscis, which has just separated from the collar; 7v. /, 2, food-grooves of first and second 



right arms; x., problematical tissue of collar-canal; /.«.., lateral nerve, originating from the central 



nervous system (c.«..y.); ovd.r., pigment in epidermis indicating the median edge of the right oviduct. 

 Fig. 48. — g-S-, outer edge of gill-slit; cc. e., fold of epidermis into which the collar-canal opens in fig. 49. 

 Fier. 4c). — C.C.C., external opening of collar-canal; x, problematical tissue of collar-canal, extending to 



base of oral epidermis of operculum. 

 Fig. 50. — This and figs. 51 — 53 shew both parts of the metasome, the ventral half giving origin to the 



stalk (st.), and containing the second stomach. 

 Pig. 51. — The collar has just separated from the metasome, but a part of its free anterior edge still 



connects the base of the fifth arm (R. j) witli the operculum (op.): — p.i'.\ edge of termination 



of posterior stalk-vessel on the alimentary canal. 

 Fig. 52. — The operculum (op.) is no longer continuous with the last arm (R.j). The stalk-vessels are not 



easy to distinguish from one another in the distal part of the stalk, but the zigzag vessel (a.v.}) 



there shewn is probably part of the anterior vessel. 

 I*"'ö- 53- — The part of the body-cavity (ö.c.^b.) extending into the loop of the alimentary canal in figs. 



50 — 52 is about to open into the general metasomatic cavity. 

 Fig. 54. — Longitudinal section of coenoecium through an orifice(É'.): — ^/., peristomial filament (Zeiss, A). 

 Fig. 55- — • Transverse section through the coenoecium (Zeiss, C). 

 Figs. 56 — 58. Frontal sections of a bud (transverse to its long axis) (Zeiss, F). 

 Fig. 56 passes a short distance dorsally to the point where the intestinal limb of the alimentary canal (int.) 



opens into the stomach (stom.). Both parts of the canal are contained in a common peritoneal 



investment (//.). 

 Fig. 57 is taken more dorsally than the last. It shews the origin of the dorsal -|- ovarian vessels (ov.v.) 



from a reflection of the peritoneum of the alimentary canal. 

 Fig. 58 is the next section on the dorsal side of fig. 57. The two roots of the dorsal vessel (d.v.) have 



united, and the ovarian vessels (ov.v.) are being given oiT from the common trunk. 

 Fig- 59- — Frontal .section of an older bud (Zeiss, Y). The proboscis (p.) lies asymmetrically : — cc, right 



collar-canal, the emargination on the left side being merely the interval between the operculum 



(op.) and the metasome: g.s., developing right gill-slit. 



yriu' figiires have heen rcduced '/^]. 



