CONTEIBUTION TO KNOWLEDGE OF RHABDOPLEURA. 645 



PLATE XL. 



Fig. 1. — Portion of one of the tentaeuliferous arms of Rhabdopleura 

 Normani denuded of its soft tissues, except at the extremities of two 

 tentacles (c), in order to expose the cartilaginoid skeleton of the axis and 

 filaments, a. Axis. b. Gill-filaments or tentacles, c. Soft tissues still ad- 

 herent to extremity of two tentacles. 



Fig. 2, — Diagram of a portion of the same skeleton. 



Fig. 3. — Base of the skeleton of a tentacle, after addition of acetic acid. 



Fig. 4. — Skeleton of the free end of a tentacle, after acetic acid. 



Fig. 5. — A bit of the skeletal cord of the polypide stalk, a. Showing the 

 same structure as the skeleton of the tentacles, b. Showing fusiform muscular 

 fibre-cells on one side of the cord. 



Fig. 6. — A portion of the polypide stalk of a fresh specimen, showing the 

 skeletal cord within, broken up (by pressure ?) into transverse discs, a. Outer 

 epithelium of the stalk, b. Skeletal cord. 



Fig. 7. — A polypide seen from the left side, the arms incompletely ren- 

 dered. The specimen here drawn was one of seven observed, which were 

 provided with a well-developed testis, a. Buccal-disc. b. Tentaeuliferous 

 arms. c. Intestine, d. Polypide's stalk, e. Anus. /. Testicular sac or 

 testis, g. External orifice of the same near the anus. 



Fig. 8. — Ripe motile spermatozoa, discharged from the testicular sac of the 

 animal drawn in Fig. 7. 



Fig. 9. — Testicular sac of another individual. 



Fig, 10. — Blind end of a third testicular sac, showing corpuscles a, which 

 appear to be sperm-blastophor cells. 



Fig. 11. — Diagram showing the disposition of the skeletal elements in a 

 polypide of Rhabdopleura. a. Buccal-disc. b. Skeleton of the arms. c. Its 

 continuation around the thorax, d. Skeleton of the stalk, e. Anus. 



Fig. 12. — Drawn from a living specimen of Rhabdopleura under the com- 

 pressorium, to show the body cavity, c. Polypide stalk, g. c. Gastric cavity. 

 B. c. The body cavity or coelom. e. Aboral region of abdomen, ax. Axial 

 skeletal cord of the stalk, ct. Connective (mesoblastic) tissue cells, e-ps. 

 Deric epithelium, epg. Enteric epithelium. 



PLATE XLI. 



Fig. 1. — Pigmented epidermic cells, in natural grouping, from the polypide 

 stalk of Rhabdopleura Normani. a. A brown-coloured cell in course of 

 dissolution, b. A similar black cell. 



Fig. 2. — An unoccupied or " permanently closed" chamber, b, of the axial 

 tubarium, with portions of two others, a and c. d. The pectocaulus travers- 



VOL. XXIV. NEW SKR. X X 



