490 Prof. A. Dendy. On a Pair of Ciliated Grooves 



than the right, owing apparently to the great development of the 

 right ganglion habenulse, which projects into the brain-cavity and 

 more or less blocks up the angle between roof and side wall. 

 Posteriorly (fig. 6) they appear to terminate as grooves at about 



FIG. 6. 



the level of the hinder margin of the posterior commissure, but a 

 band of long columnar cells appears to be continued backwards for a 

 short distance after their groove-like character has disappeared, so 

 that we find such a band on either side, bordering the narrow opening 

 between the iter below and the cavity of the choroid plexus of the 

 mid-brain above. 



The most striking difference as compared with the New Zealand 

 Ammoccete concerns the arrangement of the choroid plexus of the 

 mid-brain, which no longer dips down into the iter in the form of a 

 deep, continuous, vertical septum (compare figs. 3 and 6). (Such a 

 septum is, however, simulated in the sections by a mass of granular 

 material containing what look like nuclei irregularly scattered through 

 it. This appearance, which is not represented in the figures, suggests 

 that the septum has undergone degeneration, or possibly the granular 

 mass is simply a coagulum containing the remains of cells shed from 



