PLATE VII. 



Fig. 1. Portion of the coencecium of Cephalodiscus, 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 (hc), which lies under the 

 thick hypoderm (lip) between the plumes {hr). The coUar 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 {mf) of the 

 mouth have been included in the section, and the radiate muscles [hsni) 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 hs; 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 {ce) lies ventrally. A 

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



