89 



I have unfortunately been unable to trace the stalks of the males into continuity with 

 those of the neuters. But it is a striking feature of this species that there occur, here and there 

 in the colony, discoidal masses of tissue from which originate a number of stalks (PI. Mil, 

 fig. 94). Somewhat similar masses occur in C. gracilis, in which it is not difficult to ascertain 

 that the mass in which a number of stalks unite represents the budding region of an old stalk, 

 as may be seen by referring to the group of buds shewn in PI. I, fig. 4. 



It may thus be inferred, with a reasonable degree of probability, that the union of a 

 number of stalks in a common di.sc (fig. 94) implies that all the individuals represented by these 

 stalks are the blastozooids produced by a single budding individual. I am not in a position to 

 shew that some of these stalks belong to males and others to neuters, but I regard it as in 

 the highest degree probable that this is the case, and that the nutrition of the male takes 

 place by means of the union of its vessels with those of a neuter individual (or individuals) 

 though the common stalk-base. 



The state of preservation of the material is not suitable for the detailed examination of 

 the vessels of the stalk ; but I have convinced myself of the existence of both anterior and 

 posterior stalk-vessels, as in other species of Cephalodiscus. There is also evidence that a vascular 

 continuity between the stalks of different individuals does exist in the .stalk-bases. In one case 

 it appeared that the posterior vessel of a stalk passes into the interior of the stalk-base, and 

 travels, in the middle of the cavity of that structure, far enough to underlie the base of the 

 next stalk. The appearances suggest the exist of a vascular plexus in this position, and there 

 is some evidence that the ve.ssels of other stalks communicate with this plexus. The anterior 

 vessel of the stalk first alluded to can be traced as far as the basement-membrane of the basal 

 ectoderm of the common disc, although its exact mode of termination is uncertain. 



The principal difficulty in this view of the nutrition of the male zooids is the large size 

 of the dorsal vessel (PI. VIII, figs. 86, 87). It has been argued above that this vessel, in the 

 female Cephalodisctis, is a nutritive structure which conveys the products of digestion to the 

 ovaries. The vessel in question is certainly not less developed in the male than in the female, 

 and yet it starts from a stomach-region which is so vestigial that no stomach can be discriminated 

 from the rest of the alimentary canal. A further difficulty is that I have been unable to discover 

 any vessels from which the dorsal vessel could derive its blood. 



It is not inconceivable that the alimentary canal, though vestigial as a digestive organ, 

 might be capable of taking in some nutritive secretion discharged by the neuter individuals into 

 the cavities of the coenoecium. The mouth of the male is sufficiently well developed to make 

 this possible. But any hypothesis of this kind could hardly be accepted without more definite 

 evidence in its favour; and it seems more reasonable to look elsewhere for an explanation of 

 the large size of the dorsal vessel. 



The explanation which appears to me most probable is that this receives its blood from 

 the posterior vessel of the stalk and of the proximal jiart of the body, and that its large size 

 adapts it for acting as a reservoir of blood. I have not been able to demonstrate any continuity 

 between the two vessels in question ; and indeed the posterior .stalk-vessel in passing forwards 



SinoGA-EXPEDITIF. XXVt/'/V. 12 



