CEPHALODISCUS. 109 



anterior portion (Fig. 78). It is moreover continued as a nervous 

 tract along the dorsal side of each arm. 



The pedicle is a process from the ventral surface. It is said 

 to be largely filled with longitudinal muscular fibres, but it appears 

 to contain a prolongation of the posterior body-cavity. Buds 

 are formed upon its terminal portion. From one to three buds 

 are found upon almost all full-grown individuals. The endo- 

 dermal tissues of the parent do not extend into the pedicle and 

 play no part in the formation of the bud, the alimentary canal 

 of the latter being entirely formed by an invagination of ecto- 

 derm. 



Cephalodiscus has, in its proboscis and in close contact with the noto- 

 chord, structures corresponding to the pericardial sac, glomerulus, and 

 central blood-sinus (heart) of the Balanoglossida. 



The pericardial sac is at the anterior end of the notochord and contains 

 the heart in its interior. Blood vessels have been made out in other 

 parts of the body as spaces the walls of which are probably formed 

 by the walls of the mesodermic cavities, or they may be spaces between 

 the same structures and the ectoderm or.endoderm. 



Free eggs and embryos are found in the tubes of some species. 

 The ova are of a fair size and contain a considerable quantity of 

 yolk. The cleavage is complete and the embryos leave the colony 

 at an early stage as ciliated planulas. 



The following species are known. C. dodecalophus M'Intosh, with 12 

 arms, with end bulbs and vesicles ; cavity of tube continuous ; Straits of 

 Magellan, 448 metres. C. levinseni Harmer, with 12 arms, without end- 

 bulbs or vesicles ; cavities of the tubes divided up into chambers, one for 

 each zooid ; sea between Japan and Corea, 183 metres. C. gracilis Harmer, 

 very small ; with 10 arms, apparently without end-bulbs and vesicles in 

 adult ; E. coast of Borneo, reef. C. sibogae Harmer, male-colony only 

 known, with dimorphic individuals (see p. 108) ; S.E. of Celebes, 

 75-94 metres. C. nigrescens Lankester,* colony large and massive, nearly 

 transparent, with tubes projecting from its surface, each tube being cut off 

 from the rest and containing one full-grown zooid ; the zooids are deeply 

 pigmented and large (4' 5 mm. X 1 mm.) and have 6 to 8 pairs of arms 

 which are without terminal swellings ; each colony contains male, female, 

 and hermaphrodite individuals, the latter having one ovary and one testis ; 

 Antarctic Ocean, in 100 fms. 



The genus Ehabdo pleura^ Allman must also, in view of Fowler's 



* Proc. Roy. Soc., 1905, 76 B, p. 400. 



t Allman, Q.J.M.S., 9, 1869, p. 57. Sars, Q.J.M.S., 14, 1874, p. 23. 

 Lankester, Q.J.M.S., 24, 1884, p. 622. Fowler, Proc. Roy. Soc., 52, 1893, 

 p. 132, also in Leuckart's Festschrift, Leipzig, 1892, p. 293, and Q.J.M.S., 

 48, 1904, p. 23. Schepotieff, A. Zur Organisation von Rhabdopleura, 

 Bergens Museums Aarbog., 1904, No. 2, and Zool. Anzeiger, 28, 1905, p. 795. 



