PLATE VII. 



Fig. 1. Portion of the ccenoecium of Cej)halodiscus, about natural size, tinted as in the 

 spirit-preparations. 



Fig. 2. Transverse section of a pedicle of an unstained specimen, showing a somewhat 

 different arrangement of the folds of the basement- tissue and the central 

 muscular fibres ; letters as before ; x 350. 



Fig. 3. Oblique section of the chief area of the nerve-tissue («c), which lies under the 

 thick hypoderm (hp) between the plumes (br). The collar spaces {cv) lie 

 next the basement-tissue, bounding the nerve-centre internally, and a trace 

 apparently of the notochord is observed at c. Some of the folds (m/) of the 

 mouth have been included in the section, and the radiate muscles (bsm) of the 

 buccal shield are observed on the left ; x 350. 



Fig. 4. Transverse section of the same bud as in PI. VI. fig. 5, somewhat behind the 

 former. The body-cavity (co) now shows the rudimentary generative organs 

 (ov), the rectum (r), and the oesophagus (ce) in section. The collar spaces (cv) 

 are distinct, and the post-oral lamella (pi) is seen on the right. The position 

 of the buccal shield is indicated by the letters bs ; x 210. 



Fig. 5. Transverse section of the same bud posterior to the former, and the three regions 

 of the alimentary canal now occupy the body-cavity, viz., r, the intestine; 

 vt, the stomach, while what is probably the pharynx (a?) lies ventrally. A 

 collar pore is observed at cp; pi, post-oral lamella ; other letters as before.-. 



