Cytological studies on the spinning glands of Platyphylax etc. 415 



Some sections of glands active for five hours showed a number 

 of small blunt processes projecting from the surface of the gland 

 into its lumen (Fig. 26). Each is seen to contain a number of darkly 

 staining bodies somewhat similar to, but larger than, those along the 

 margin of the cell of two and one-half hours of activity (Fig. 25). These 

 projections remind us of the secretory processes which are often found 

 on the free surface of the intestinal epithelium of insects. 



After twenty-four hours activity one change at least is quite no- 

 ticeable, and that is the slight increase in thickness of the cytoplas- 

 mic -like layer just outside of the inner membrane (Fig. 27). The 

 light brown layer varies, as before, in thickness in different parts of 

 the sections; its outer surface is irregular. Referring again to the layer 

 just outside the inner membrane we find that it has increased a little 

 in thickness and is quite similar in structure to the cytoplasm which 

 lies on the other side, i. e., within the cell. It also shows a number 

 of blunt processes which project slightly into the lumen of the gland. 

 The outer surface of these processes is more deeply stained than the 

 rest and the larger ones have this darkened portion drawn out into 

 short strands, many of which connect with the border of the light 

 brown layer. In many parts of the sections where this layer has 

 been pulled some little distance from the gland, long strands were seen 

 between the two, which, if the layers were not too widely separated, 

 connected the one with the other. These strands were very irregular 

 and stringy. 



In glands from larvae which had been active for forty- eight hours 

 no great changes were noticed, the only one we would record being 

 a slightly greater thickness of the layer just outside of the inner mem- 

 brane. The lobate processes which we noticed in the twenty-four hour 

 gland were here more pronounced; a few stained very densely and were 

 nearly homogeneous. 



In glands which had been active for one hundred and twenty 

 hours (Fig. 28) we noticed that at all places along the inner margin 

 of the cells there was a great similarity. Just within the inner mem- 

 brane there is a narrow band of cytoplasm which is lighter in color 

 and of less density than that adjacent to it; in this marginal layer 



