84 



appears to exist between the narrow pigment-line of the proboscis and the oviducts in the 

 constitution of the pigment. It is not impossible that the pigment of the oviducts has an 

 excretory function, with which its resistance to sohition by spirit is quite in accordance. Fig. 46 

 (C gracilis) gives some evidence that the pigment can be discharged to the exterior froni 

 the aperture of the oviduct; but it is quite possible, in the absence of further evidence, that 

 this appearance is unnatural. 



C. sibogae. 



The most interesting outcome of my work on the "Siboga" material is the discovery 

 of the males of Cephalodiscus. It is of course impossible to say how far the facts observed in 

 C. sibogae will be found to apply to other species; but in view of the very small amount of 

 anatomical differences, in other respects, between species which are at first sight extremely 

 unhlve one another, I suspect that what is true of C. sibogae will be found, with modifiications, 

 to be of general application in the genus. 



The ordinary zooids of C. sibogae are usually completely slerile or neuter individuals 

 (PI. I, fig. 3), though in immature blastozooids (PI. XIII, fig. 184) the reproductive organs 

 may be represented by a pair of minute vestiges {g.), similar in position to the ovaries of the 

 other species. I am inclined to regard the neuters as modified males rather than as modified 

 females, since I have found at least one case in which functional testes appear to be pre.sent 

 in a specimen which otherwise resembles a neuter. 



In the tangled masses of zooids which occur in the basal jelly of the colony are tound 

 considerable numbers of individuals of an entirely different appearance (PI. VII, figs. 72 — 76); 

 and these are the males. While shewing the general Cephalodiscus structure in an unmistakeable 

 way, the males have very remarkable peculiarities of their own, the most striking of which is 

 the complete want of any arrangements for taking food. This is indicated by the absence of 

 tentacles and of the operculum, and by the vestigial character of the alimentary canal. 



A fuU-grown male, drawn to the same scale as the neuter individual, fig. 3, is represented 

 in fig. 75, from which it will be seen that there is not much difference in size between the 

 males and the neuters. This individual was cut into frontal sections, some ot which are shewn 

 in figs. 80 — 89 (PI. VUI). The proboscis (/.) is rather small, but it has the same relations 

 as in normal Cephalodiscus zooids, and even possesses the characteristic line of red pigment 

 across its ventral lobe. The collar is produced into a single pair of arms (i?. a-. and L. a.), 

 which possess no tracé of tentacles. The epidermis of these curious arms ot the male is, except 

 for a short region at the base, almost entirely constituted by enormous numbers of refringent 

 vesicles (PI. IX, fig. 99), similar to those which occur in the terminal knobs of the arms of 

 the female C dodecalophus or in those of some of the arms of C. gracilis. The arms seem to 

 be subject to great variation in length. In the individual shewn in fig. 75 they are relatively 

 short, but in other cases they may be at least twice as long. The refringent vesicles make their 

 appearance at a young stage, and there is some evidence that they may become used up in 

 some of the older males. In other cases, however, they are still present in undiminished numbers 

 in individuals in which the testes are fully developed. 



