-24- 



Figs. 5 e-h. Fig, 5 m shows the extent to v/hlch the gland is 

 completely divided by the partition fm.l.), and also the position 

 of the gland in relation to the gill arches (v. a., 2-5). The 

 cilia are omitted from this figure. In all the sections posterior 

 to the duct, as seen in Fig. 5 j, there are three distinct cili- 

 ated chambers. The median ciliated chamber (m.c.h.), occupying 

 the central division of the gland, is triangular in cross section, 

 and is partially divided into two chambers by the median lamella 

 (m.l.) which rises from the middle of its ventral wall. Into 

 each half of the median ciliated chamber empty one of t^e large 

 and one of the small groups or cylinders of gland cells. Tae 

 smaller cell group, as has been said, at this stage is still 

 in a rudimentary condition. 



The lateral ciliated chamber )l.c.h,) is crescentic 

 in cross section, the lesses curve of the orescent being formed 

 by the ciliated cells, the greater curve by the cover cells. 

 Into the lateral chamber empty a large and a small group of gland 

 cells. Dorsal to the gland are the tvro large blood vessels 

 (art.) and close above these the floor of the pharynx, with the 

 ventral ciliated groove (v.c.g.), now much diminished in depth. 

 Fig, 5 k is of a section near the posterior end of the gland, 

 passing through the upcurved portion. The reference line m.ch, 

 begins in the cavity of this upwardly bent part, which is cut 

 through at the point v/here it is continuous with the central 

 ciliated chamber of the gland. A section just anterior to this 



