EEfORf ON CEPHALODISCUS DODECALOPHUS. 31 



The next slice, indeed, shows the muscular fibres filling up the entire central area of the 

 pedicle, whUe the septum proceeds only a short distance inwards from the dorsal wall. 

 A somewhat radiate arrangement of the fibres also takes place, and is best marked 

 ventrally in transverse section. After a short course the fibres terminate on the h}q3u- 

 dermic covering of the end of the pedicle, which at this stage presents proportionally 

 great development. The immature pedicle of the bud thus diS"ers from that of the 

 adult in the outline of the basement-layer, which is simply reniform in transverse 

 section, whereas that of the adult presents two maxillae on each side ventrally, and a 

 median dorsal fold. 



Externally, as indicated, the short pedicle almost immediately follows the anterior 

 dorsal projection of the body ; and as a peculiar curvature of the latter has now taken 

 place, the tip of the pedicle scarcely projects beyond the margin of the disk. Shortly 

 after reaching the stage just described, and while the symmetrical series of filaments on 

 each side of the plumes is quite small, the bud sejaarates from the parent. The pedicle 

 and its sucker-like hjrpodermic termination are fairly developed ; and as soon as it is 

 detached (and sometimes before) a little bud appears near the tip. Thus the increase of 

 the species by budding alone must be remarkable, even comparatively young forms 

 giving rise to a succession of buds. One or two buds are most frequently seen on 

 the pedicle of the adult, though occasionally three or more exist. 



Shortly before obtaining freedom the buds in some cases present a striking 

 resemblance to certain stages in the buds of Rhabdopleura, as shown by Professor 

 AlLman. Thus in examples in which the first pair of plumes are very long and the 

 succeeding short, while the stalk is in a state of extension, a condition closely 

 approaching Professor Allman's figure 8 ' is produced. 



The buds thus differ from those in Rhabdopleura in attaining freedom nn reaching a 

 certain stage, but both probably arise in a similar way, two at least of the embryonic 

 layers taking part in their production. The first layer is represented \>y tlie dermal 

 layers, nervous centre, buccal region, and the rectum, and the second by the skelcto- 

 genous tissue and longitudinal muscles. The presence of the third layer, as already 

 mentioned, is more doubtful, though it is possible that the cells and globules oltserved 

 towards the end of the pedicle may be of hypoblastic origin, being derived from the 

 central region of the alimentary canal. The sections of the younger buds present, in 

 the arrangement of the alimentary canal, a close resemblance to the young PediceUina, 

 as shown by the careful researches of Dr. Barrois and Mr. Harmer. The position of the 

 ganglion in the diagram* of the latter would nearly correspond with the nerve-centre 

 in Cephalodiscus. 



In Loxosoma the position of the buds is very different, viz., in thu region of the 

 stomach, and there are never more than two. 



1 Quart. Joum. Micr. Sri., pi. viii. ' Quart, /.urn. .Micr. Sex., pi. xxii. fig. 19. 



