POLYPIDES OF CEPHALODISCUS HODGSONI. 53 



The polypides bear a tolerably close resemblance to those of C. dodecalophus, 

 but they are a little larger, measuring 2 mm. from the posterior end of the 

 visceral mass to the front of the buccal shield, and about 2' 5 mm. to the ends 

 of the plumes, whereas in C. dodecalophus the corresponding measurements are 1 5 

 and 2 mm. The only colour which the polypides possess is that of the red line 

 of the buccal shield, and the red pigment of the gonad ducts. 



The " body " is rather more elongated and less bulbous than that of C. dode- 

 calophus, and the stolon arises relatively farther from the shield. The shape of the 

 body is largely determined by the stomach, which is globular and dilated, as 

 in C. dodecalophus, and not compressed as it is in C. nigrescens. The stolon is 

 distinctly longer and more slender than that of C. dodecalophus, and in an average 

 state of contraction measures 2 mm. or less. It is sometimes found curving 

 forwards toward the shield, but if extended it is usually directed parallel with the 

 long axis of the body (see figs. 49 and 50, plate 6). The stolon at its maximum of 

 extension measures 4 mm. or more (fig. 51). 



The buds are usually two in number, a large and a small bud, but 

 occasionally as many as four are met with at the end of the same stolon. When 

 a bud remains attached to its parent until it attains a considerable size, it 

 develops a bud of its own. 



The number of plumes is in the majority of cases twelve. Each plume axis 

 terminates in a bulbous enlargement with refractive beads, particularly in individuals 

 of moderate size only. 



One specimen was found having a body shaped like a short sausage, with an 

 extremely slender and elongated stalk arising from one extremity. No plumes, 

 buccal shield, post-oral lamella, mouth, gill-slits nor gonad ducts are to be 

 distinguished (fig. 52). This solitary specimen is of interest in connection with the 

 remark made by Harmer (10, p. 93) that in C. gracilis the " degeneration of a zooid 

 begins by the throwing off of the proboscis and collar, leaving the metasome, with 

 the alimentary canal, attached to the stalk," and that " degeneration of the zooids 

 is of frequent occurrence, and is usually not succeeded by any regeneration of lost 

 parts." The plumeless polypide of C. dodecalophus figured by M'Intosh as an 

 "abnormal specimen" has no stalk (19, fig. 4, plate 3). 



Most of the polypides are females ; two out of the fifty or more specimens 

 examined are hermaphrodite ; the rest are males. The sexes of the polypides 

 cannot with certainty be distinguished except by dissection, but as a rule the red 

 pigment of the gonad-ducts is distinctive of the female ; at all events it is more 

 strongly marked in the females than in the males. There are no neuters, except 

 perhaps the plumeless polypide mentioned above, the anatomy of which was not 

 worked out. Further details of the plumes, stolon, and gonads, and the characters 

 of the shield, buds, etc., are given under special headings in the pages that 

 follow. 



