12 



ZOOLOGY 



SECT. 



Rhabdopleura (Fig. 714) occurs in colonies of zooids organically 

 connected together, and enclosed in, though not in organic con- 

 tinuity with, a system of branching membranous tubes connected 

 with a creeping stolon. The collar-region bears a pair of hollow 

 arms each carrying a double row of slender tentacles the whole 

 supported by a system of firm internal (cartilaginous ?) rods. 

 There are collar-pores and proboscis-pores. The " notochord " and 

 the nervous systems resemble those of Cephalodiscus. A single 

 testis has been found, opening on the exterior by a pore situated 

 near the anus. The female reproductive apparatus is unknown. 



FIG. 713. CephalodiSCUS. Diagram of longitudinal section, a. anus ; be 1 , ccelome of pro- 

 boscis ; be' 2 , ccelome of collar ; ftc 3 . ccelome of trunk ; int. intestine ; m. mouth ; nrh. supposed 

 notochord ; n. s. nerve-strand ; op. operculum ; ces. oesophagus ; ov. ovary ; ovd. oviduct ; ph. 

 pharnyx ; p. p. proboscis-pore ; ps. proboscis ; st. stomach ; stk. stalk. (After Harmer.) 



Cephalodiscus, of which there are twelve species, has been found 

 at various widely separated localities in the Southern Hemisphere 

 (Straits of Magellan, Borneo, Celebes, the Antarctic) : species 

 occur off the coast of Japan and Korea. Some live in shallow 

 water : none have been found at a greater depth than 245 fathoms. 

 Rhabdopleura has been found at moderate depths in Norway, 

 Shetland, the North Atlantic, France, the Azores, Tristan 

 d'Acunha, Celebes, and South Australia. It seems doubtful if 

 more than one species occurs. 



