Mastermax (97, 2, p. 351) states that the cells of the notochord of C. dodecalophus are 

 ciliated internally, and that it may contain in its lumen a rod of mucus. In a later memoir 

 (03, p. 718) he describes a vacuolated or "chordoid" appearance at the anterior end of the 

 organ. I have observed a stained appearance in the lumen of the notochord in this .species 

 which may indicate the presence of mucus, but I feel e.\tremely doubtful with regard to the 

 existence of cilia, and I am not convinced that there is sufficient justification for speaking of a 

 chordoid modification of the tip of the organ. 



The large relative size of the notochord in the buds of C. dodecalophus (PI. XIII, fig. 

 173) — a fact already noticed by M'Intosh (87, p. 28) is of considerable interest as indicating 

 the morphological importance of this structure. It is further noteworthy that the organ is specially 

 large in the buds of Rhabdopleura^ as appears from the observations of Fowler (04, PL III, 

 fig. 15). In the adult condition it retains its greatest relative size in C. levinseni (figs. 33, 23, 

 24, 113) where its tubular nature is specially obvious. In the more delicate C. gracilis (figs. 

 44, 64) and C. sibogae (PI. VIII, fig. 93) the notochord is small; and in unfavourably orientated 

 sections it is not always easy to demonstrate its existence. There is no doubt, however, of its 

 presence in all the species which I have investigated, and it may be detected even in the males 

 of C. sibogae (PI. VIII, figs. 82, 83). 



The homology of the notochord of Cephalodiscus with that of the Enteropneusta was 

 at one time denied by Masterman (97, 2, p. 35 1; 97, 3), who has, however, more recently 

 (99, 2, p. 362) admitted that it corresponds with the "vermiform process" of certain Entero- 

 pneusta. WiLLEY (99, I, p. 237) had shortly before maintained the same view. 



It appears to me that it is unnecessary to suppose that the notochord of Cephalodiscus 

 corresponds merely with the vermiform process. It is true that on a former occasion (97, p. 343) 

 I pointed out, in answer to Masterman's statement that the notochord of Cephalodiscus 

 differs histologically from that of "every other notochord yet described", that it did not differ 

 histologically from the anterior part of the notochord of Schizocardium and Glandiceps known, 

 frf)m Spengel's description, as the vermiform process. But I also called attention to the small 

 size of Cephalodiscus^ a fact which might be expected to be correlated with some simplification 

 of the organs as compared with those of the Enteropneusta. The relation of the notochord of 

 Cephalodisctis to the pericardium and to the proboscis-pores appears to me to lend no sujjport 

 to the view of Willey and Masterman that the organ corresponds with the vermiform process 

 alone. The process in question, as figured by Spengel (93, PL XII, fig. 2 and PL XX, fig. i), 

 lies entirel)- in front of the region of the pericardium and of the proboscis-pores, while the 

 notochord of Cephalodiscus extends no further forward than this region. As moreover, the base 

 of the notochord agrees, in its relation to the upper lip and to the ventral part of the anterior 

 body-cavity, with the base of the "Eicheldarm" in the Enteropneusta, it seems to me reasonable 

 to .suppose that the notochord of Cephalodiscus corre.sponds with the entire "Eicheldarm", and 

 not with the narrow anterior portion of it whose occurrence is limited to a small proportion 

 of the species of Enteropneusta. 



SIHOG.\-EXPEDITIE XXVI to. 



