244 W. G. KIDEWOOD. 



At a time wlien the fifth plumes are just appearing (k, 5) 

 the first plumes point well forward and not laterally, the 

 fourth plumes are twice as long as broad, and pinnules are 

 making their appearance on the third plumes. It would 

 seem that the fifth plumes grow very slowly, for in the 

 specimen figured in text-fig. 9, l, the fifth plume on the one 

 side is not much longer than broad, and on the other side it 

 is even less developed, and yet the pinnules on the first pair 

 of plumes are digitate processes, twice as long as broad, and 

 pinnules have already made their appearance on the fourth 

 plumes. The first four pairs of plume-axes are now almost 

 of the same length. 



In all of the buds of Cephalodiscus gilchristi, except 

 the very young ones, the surface of the '^ body " is closely 

 studded over with refractive beads similar to those which 

 occur on the end-bulbs of the plumes of Cephalodiscus 

 dodecalophus and Cephalodiscus hodgsoni. In the 

 present species the refractive beads occurring on the plumes 

 are negligible ; the beads occur mostly on the general 

 surface of the body, and, in the adult particularly, on the 

 upper surface of the anterior margin of the buccal shield 

 (see description of Cephalodiscus gilchristi, 'Marine 

 Investigations in South Africa,' vol. 4, 1906, p. 184). The 

 refractive beads are not shown in text-fig. 9. 



Buds in which the fifth plumes are more advanced than 

 in L, and buds iu which the sixth plumes are developing I 

 have been unable to find. This is not without significance 

 when taken in conjunction with the fact that in the material 

 of Cephalodiscus nigrescens I found only one late bud 

 showing the plumes more advanced than is represented in 

 text-fig. 7, J, and with the fact that in Cephalodiscus 

 hodgsoni the later stages in plume development, showing 

 the development of the sixth plumes, are not rare. The 

 species gilchristi and nigrescens have tubaria in which 

 the polypides are isolated, and live in separate tubular 

 cavities, which open individually on the surface, and do not 

 communicate the one with the other. The species hodgsoni. 



