-50- 



Pigs. 6 a and 6 "b, but the fibrosis tissue is shown In all the 

 figures of this stage. 



Pig. 6 b represents a section cut a short distance 

 anterior to the duct, at the point b Fig, 6 k, and about corres- 

 ponds to Fig. 5 h of the preceding stage. The ciliated grooves 

 at this point have united to form a single deep groove which is 

 spread out at the bottom to form the side pockets (p.) described 

 in the preceding stage. The lateral and median pairs of cell- 

 groups have approached each other until their adjacent groups 

 are nearly or quite in contact; at the same time the ciliated 

 l?.yer (f.l.) has increased somev/hat in length, and, at its dorso- 

 median angle (at the end of the lines f.l.. Fig. 6b), its cells 

 have changed from the tall columnar with small, round nuclei 

 to short cells, almost completely filled with their large oval 

 nuclei and resembling the cells that lie close to the openings 

 (c.) of the groups of the gland cells. It is this group of cells, 

 lying in the dorso-median portion of the ciliated layer, that 

 separates into two about equal parts, a little farther posterior- 

 ly, to connect the gland v/ith the deep ciliated groove in the 

 manner described in the preceding stage and shown in Figs. 5 h-i 

 of that stage and in Fig, 6 c of the stage now under discussion. 

 The ciliated layer is somewhta folded, as though it had Increased 

 in length very raj^idly, or I'ad been compressed by the shrinkage 

 of the connective tissue (c.t.) surrounding the gland. There is 

 considerable space at this point between the pharynx and the 



