26 



specimens) by a pair of large ovaries (fig. 22, ov. r.^ov. /.), each of which leads by a pigmented 

 oviduct [ovd^ to its external orifice, situated 011 the dorsal surface of the metasome, not far 

 behind the end of the central nervous system. Between the pharynx and the rectum, in the 

 middle line of the body, and consequently between the two ovaries lies the dorsal vessel [d. z'.), 

 which is the largest blood-space of the animal. 



The above are the more conspicuous anatomical features of the zooid, and further 

 details may be left for the Sections dealing with the several organs. 



VII. PROBOSCIS. 



The general characters of the proboscis or protomere, in the several species, have 

 already been described (p. -17); and in particular attention has been called to the extraordinary 

 proboscis of C. levinseni. The proboscis of that species is of remarkable mobility, owing to 

 the presence of an unusually long neck or proboscis-stalk. The neck may be stretched out 

 in the direction of the principal axis of the body (figs. 23, 24), carrying the discoidal part of 

 the proboscis or "buccal disc" into an endless variety of positions. In fig. 24, the disc has the 

 form of a somewhat complicated umbrella; but it may assume almost any position, and is very 

 commonly turned upside down, so that its dorsal edge looks ventrally, and its ventral edge 

 dorsally (figs. loi, 139), by the rotation of the neck round its longitudinal axis. These 

 remarkable attitudes of the proboscis may make it a matter of some difficulty to interpret the 

 sections of the anterior end of the animal ; and the complication is often further increased by 

 the retraction of the thick anterior wall of the disc into a strong fold (figs. 23, 24, 139), a 

 habit which may also be noticed in some specimens of C. dodecalophits. The sagittal section, 

 fig. 34, is one of the cases in which the proboscis has its normal position ; but the extensible 

 character of the neck is even here indicated by its thickness and by the folds in its walls. 



In spite of these peculiarities of C. levinseni the proboscis has the same essential 

 characters in all the species, not excepting the male individuals of C. sibogae. It may be 

 remarked that the term "buccal disc", which has usually been employed in describing this part 

 of the animal, is not exactly synonymous with "proboscis". The latter is a morphological term, 

 indicating its relation to the similar organ in Balanoglossus. The "buccal disc", however, may 

 include dorsally a part of the collar (fig. 42) although in C. levinseni it consists of the anterior 

 end of the proboscis, the posterior end of which, with part of the collar, constitutes the neck 

 or proboscis-stalk. 



The relations of the collar to the proboscis will be described below, in the Section dealing 

 with the collar. The proboscis itself invariably terminates in front in the enormous buccal disc, 

 which is flattened in an antero-posterior direction. The anterior wall of the disc is composed 

 principally of much elongated gland-cells, which give this wall of the proboscis a great thickness. 

 As has been pointed out above (p. 9) there can be little doubt that the gland-cells have the 

 function of secreting the gelatinous coenoecium. At the base of the gland-cells may be seen, in 



