602 



COMPARATIVE ANATOMY 



CHAP. IX 



somewhat of the consistency of cartilage. Similar skeletal pieces 



support the tentacles and their branches. 



Some insight into the chief anatomical features of the individuals will 



be gained from the figures (Figs. 472, 473). The principal differences 



between Rhabdopleura and Cephalo- 

 discus are : (1) the gill -slits are 

 wanting in the former; (2) there 

 are only two feathered tentacles ; 

 (3) the proboscis pores, i.e. the 

 pores of the coelom of the buccal 

 shield, are wanting. 



The genital organs are still 

 imperfectly known. In some speci- 

 mens a testicle tube, which runs 

 longitudinally and asymmetrically 

 along one side of the body, and 

 bulges out the body wall, has been 

 demonstrated : this tube opens out 

 near the anus. Rhabdopleura, like 

 Cephalodiscus, is a deep-sea form. 



Further research is needed be- 

 fore we can establish the exact 

 relationship of Cephalodiscus and 

 Rhabdopleura to the Bryozoa. 



Literature. 



FIG. 473. Rhabdopleura Normani, 

 median longitudinal section, diagrammatic 

 (after Fowler). 1, Tentacle of one side, in- 

 dicated by dotted lines ; 2, anterior paired 

 coelom (collar coelom) ; 3, anus ; 4, posterior 

 paired or trunk coelom ; 5, hind-gut ; 6, mid- 

 gut ; 7, buccal cavity ; 8, mouth ; 9, anterior 

 diverticulum of the buccal cavity (probosciclal 

 diverticulum) ; 10, ccelom of the buccal shield 

 (proboscidal coelom) ; 11, buccal shield. 



G. J. Allmann. On Rhabdoplcura, a new 

 form of Polyzoa, from deep-sea dredg- 

 ing in Shetland. Quart. Journ. 

 Microsc. Sc. Vol. IX. 1869. 

 G. Herbert Fowler. The morphology of 

 Rhabdopleura Normani Allm. Fest- 

 schrift zum Siebenzigsten Geburtstag R. 

 Leuckart's. 1892. 

 Sidney F. Harmer. Appendix to M'Intosh : Report on Cephalodiscus dodecalophus 



M'Intosh. Rep. Voy. of the "Challenger" Zool. Vol. XX. 1887. 

 E. R. Lankester. A contribution to the anatomy of Rhabdopleura. Quart. Journ. 



Microsc. Sc. Vol. XXIV. 1884. 



W. C. M'Intosh. Report on Cephalodiscus dodecalophus M'Intosh, a new type of the 

 Polyzoa, procured on the voyage of H.M.S. " Challenger." Rep. Voyage 

 " Challenger " Zool. Vol. XX. 1887. 



G. 0. Sars. On Rhabdopleura mirabilis. Quart. Journ. Microsc. Sc. Vol. XIV. 

 1874. 



