No. 3.] OESOPHAGEAL GLANDS OF URODELA. 95 



the vesicle, but in these glands it is difficult to explain why the 

 fluid is not discharged into the cavity of the foregut before 

 the pressure gets sufficiently high to cause a stretching of the 

 cells. A possible explanation is the viscidity of the secretion 

 owing to the large number of mucous cells in these glands. 



Fig. 4 shows a gland only moderately distended, and here it 

 is seen that the cells at the bottom, where the gland is unsup- 

 ported by neighboring glands, are drawn out flat, while those 

 at the side still retain their approximately columnar shape. 



The two kinds of cells noticed in the earlier larva may still 

 be recognized, the clear mucous cells occupying the top and 

 neck of the flask, the granular cells the sides and base of the 

 flask. The protoplasm of the latter now stains strongly in 

 haematoxylin, and exhibits a faintly striated or finely vacuolated 

 structure. This is due to the presence of prozymogen, which 

 may also be demonstrated by the use of acid alcohol, followed 

 by aqueous haematoxylin after the method of Macallum. 1 The 

 inner end of the cell between the nucleus and the lumen stains 

 but slightly in haemalum, but in sections treated with neutral 

 gentian it is seen to be filled with perfectly round, deeply stained 

 granules of zymogen. The neck of the flask-shaped gland is 

 occupied by long mucous cells of a columnar shape, which also 

 extend into the gland and form the top of the flask. In these 

 cells two zones may be distinguished, an outer protoplasmic, 

 which stains strongly and which contains a quantity of masked 

 iron, and an inner transparent and reticular. The meshes of 

 the latter are filled with a substance which stains faintly in 

 indulin, more readily in Mayer's mucicarmine. In sections 

 stained with neutral gentian many deeply stained granules may 

 be seen in the mucigenous portions of these cells. These are 

 somewhat elongated and not perfectly round, as are the zymo- 

 gen granules of the other kind of cell. Their significance is 

 not clear ; it is possible that they may indicate an imperfect 

 differentiation of the zymogenic and mucigenic functions at 

 this stage of development. 



The surface epithelium in this region of the foregut consists 

 of alternate ciliated cells and goblet cells. Tracing the foregut 



1 Journ. of Phys. Vol. xxii. 1897. 



