BEA'SLEY. 



[VOL. II. 



recognized, even to a late stage of development, as disinte- 

 grating remains in these and the other gastric glands. 



The posterior glands are simple tubes composed of a single 

 layer of large yolk-filled cells surrounding a cleft-like lumen. 

 Indeed, often it appears as if the endoderm of theforegut were 

 in several layers without any differentiation into glands 'and 

 epithelium. On careful inspection, however, it may be seen 

 that the nuclei are arranged in an orderly fashion, as if sur- 

 rounding the lumina of glands. Such an appearance is illus- 

 trated in Fig. 2. In this gland, in addition to the nuclei which 

 are clearly arranged in a row around the lumen, two others 



may be seen which are nearer the center 

 of the gland ; these are the nuclei of cells 

 which will later be found as disintegrat- 

 ing remains in the lumen. 



The flask-shaped glands do not, as one 

 proceeds caudad, abruptly give place to 

 the simple tubular glands, but there is a 

 gradual transition. 



In a larva 12 mm. in length, although 

 the caudal portion of the stomach is still 

 undifferentiated and the cells crowded 

 with yolk, the yolk has sufficiently dis- 

 appeared from the anterior portion to 

 enable the shape of the glands and the cells composing 

 them to be clearly determined. The anterior glands arc 

 now distinctly saccular, with a large lumen surrounded by a 

 single layer of cells. The yolk spherules disappear from the 

 cells of the glands somewhat more rapidly than from the sur- 

 face epithelium, which as yet contains a considerable number. 

 Notwithstanding the presence of the yolk, one can clearly dis- 

 tinguish, at this early stage, several kinds of cells, which can 

 be readily referred to their analogues in the glands of the 

 adult. The flask-shaped body of the gland (Fig. 3, a) is formed 

 of a single layer of small cells, which vary from cubical to 

 fusiform in shape and are usually convex towards the lumen. 

 The protoplasm of these cells is granular and contains one or 

 more yolk spherules. The nucleus is round or oval and rich 



gastric 

 gland, zeissapoch. 



2 mm., comp. ocular 2. 



