No. 3.] OESOPHAGEAL GLANDS OF URODELA. 93 



in chromatin. As the gland narrows into the duct (Fig. 3, b), 

 these are replaced by two or three slightly larger cells, in each 

 of which two zones may be recognized, an outer, wider, deeply 

 staining zone containing the oval nucleus, and an inner one 

 which stains but feebly. This inner zone exhibits a reticular 

 structure due to the presence of a secreted substance, probably 

 mucigen. In the more posterior tubular glands, likewise, two 

 kinds of cells may be found, similar in all respects to those of 

 the flask-shaped glands, granular cells occupying the body of 

 the gland, mucigenous cells the neck. In sections stained in 

 Reinke's neutral gentian it is found that already numerous 

 zymogen granules are present in the deeply 

 staining cells forming the body of the gland. 

 In the pancreas, also, zymogen granules may 

 be recognized long before the yolk granules 

 have entirely disappeared from the cells. 

 The epithelium of the foregut in the region 



occupied by the flask-shaped glands is com- ^ ^ a 



posed of two kinds of cells (Fig. 3, c), ciliated 



cells and cells the outer ends of which stain 



diffusely and intensely. These obviously FlG . 3 .J^ blystoma 



represent the two characteristic elements of larvai 2mm - in length; 



, c ..... .... oesophageal gland. 



the future oesophageal epithelium, the cm- Apoch. 2 mm.,com P . 

 ated and the goblet cells. Over the tubular ocular2 - 

 glands farther back there is only one kind of cell in the 

 epithelium, and this is without cilia. 



Mitoses may be observed with equal frequency in all the 

 various kinds of cell composing the epithelium and glands, and 

 all are apparently equally capable of reproduction. 



The important points to be learned from this stage are 

 that the characteristic elements of the glands are differen- 

 tiated very early, that no special groups of cells have, as yet, 

 assumed the mitotic function to the exclusion of the others, 

 and. that a portion of the glandular foregut bears a ciliated 

 epithelium. 



In a larva 14 mm. in length the foregut has advanced to a 

 considerable degree beyond the stage last described. It is 

 now shaped like a letter U, with a long proximal and short 



