91 



of the old males seem to have lost most of their vesicles; although, on the other hand, others 

 shew no trace of this tendency. 



Masterman (97, 2, p. 344) suggested that the end-bulbs of C. dodecalophus had the 

 nature of compound eyes, a function which their position makes not improbable; although he 

 subsequently abandoned that hypothesis (03, p. 725). Colf, (99) on the other hand believes that 

 the vesicles are comparable with the rhabdites of Turbellaria. Although I have not examined 

 the structures with the aid of the histological methods recommended by Cole, the suggestion 

 of this observer seems to me not improbable. If this were the case it would follow that the 

 male individuals of C. sibogae are not only the individuals which produce the spermatozoa, but 

 that they have a subsidiary function, analogous to that of the dactylozooids of Hydrozoa, of 

 producing weapons for the defence of the colony. It may be presumed that the zooids of both 

 kinds can be protruded more or less from the orifices of the coenoecium. It is not difficult to 

 imagine that the long arms of the immature and adult males, waving about in the water among 

 the plumes of the neuter zooids, might be valuable weapons of defence, on the assumption that 

 Cole's view that the end-bulbs of C. dodecalophus are rhabdite-batteries is the correct one. 



It seems to me not impossible that the remarkable "Harchen" of the epidermis of 

 Phoronis gracilis^ of which a description has recently been given by de Selys Longchamps 

 (03, p. 28, figs. 22 — 26), may be comparable with the epidermic vesicles of Cep/ialodiscus. 



XVI. BUDDING. 



The details of this process have been described b)- Mastermax (98, 2), some of whose 

 more important results may be summarised as follows. — 



The buds are formed on either side of the middle line of the parent stalk, from the 

 proximal, sucker-like extremity of that structure. A new bud may develop from the stalk of a 

 young individual which has not yet become free. The tissues of the bud are derived entirely 

 from ectoderm and mesoderm, the endoderm taking no part in the process. The coelomic cavities 

 are formed from that of the parent stalk, and in the youngest stage observed are represented 

 by a single pair of cavities, completely subdivided by a median mesentery, and continuous with 

 the cavity of the stalk of the adult. The mesentery contains a vessel which is given off by the 

 anterior stalk-vessel. The vessel contained in the bud assumes a dorsal position distally, where 

 it dilates to form the '■'subneural sinus". The proboscis early becomes conspicuous, its undivided 

 body-cavity being the distal extremity of the coelom of the young bud, although it is not 

 explained exactly how the unpaired anterior body-cavity is related to the paired coelom of the 

 more proximal part of the bud. It must be supposed from the account given, and particularly 

 from a consideration of Masterman's figures 29 and 30 that the median mesentery ends abruptly 

 before reaching the distal end, which is accordingly undivided. The alimentary canal early makes 

 its appearance as an ectodermic invagination, the orifice of which persists as the mouth. At 

 about the stage when the first pair of arms begins to be indicated externally, the enteric sac 



