c^i"j¥:-(Zi.v'^/.^\"r.^. 263 



The .iccount which we possess of Cephaiodiscus fonr.s 

 one of the Challenger Reports, .uid was written by Pro- 

 fessor W". C. MTxTosH. who made out the main features 

 of its an.itomv. It was further treated, from a morpho'.oc;- 

 icai standpoint, b\- Sipnev F. Hakmer, who pomted out 

 its remarkably close altinity to Balanoglossus. 



The most important morphological features in the anat- 

 omv of Cephalodlscus are shown in Figs. uf-i::,". 1 he 

 individuals live in colonies, m a "house" or .-.:-':av ::.":. 

 which consists of a ramifying" and anastomosing system of 

 tubes, the walls of which are composed of a semi-trans- 

 parent. s;elatinous material, whose outer surface ;s covered 

 with spinous projections. The walls of the c^-en^-ecium 

 are furthermore perforated by numerot:s apertures, which 

 allow of the ingress and egress of water. 



The adult members of a colon\' have no organic con- 

 nexion between themselves, but each one is maependent 

 and free to wander about the tunnels of the ccenctcium. 

 Although Cephalodiscus has not been studied in the li\-ing 

 condition, there is e\-ery reason to suppose that it moves 

 about in its tube bv means of the large r:,.\\!.' s':.\\'.:\ Fig. 

 i-O overhanging the mouth, bv which it can attach itself 

 to the inner surface of the tube, and then help itself 

 along bv the curious /■;■.;";. -.V which occurs ventrallv near 

 the hinder end. It thus seems probable that this pedicle 

 can be used as a sucker, but its chief function lies in the 

 production of buds which grow out from it. and eventuallv 

 become detached. Bateson has described a somewhat 

 similar sucker at the hinder end of the bodv in \oung 

 individuals of Balanoglossus iFir-'- ii5^- 



Behind and above the buccal shield there is a row of 

 twelve tentacles or branchial plumes, each possessing a 

 central stem or shaft w-hich carries numerous lateral 



