Cytological studies on tlie spinning glands of Platyphylax etc. 407 



hard to distinguish but it is undoubtedly present. It can best be seen 

 in the thinnest sections. The disappearance of the linin in glands 

 which had been fixed in sublimate, as Meves [16] holds, we doubt, 

 believing that a careful observation will reveal the reticulum in all 

 sections. 



The earliest of the active glands which we prepared was one 

 taken from a larva which had been rebuilding its case for two and 

 one -half hours; the next stage was after five hours of activity 

 (Figs. 11 and 12). There was such a slight difference in these two 

 periods that, while some minor differences could be observed, it was 

 thought best to describe them together. 



A study of a gland active for five hours (Fig. 11) shows that the 

 change from the normal gland which has taken place is in the cyto- 

 plasm and not in the nucleus. What we have said of the normal 

 gland, that the cytoplasm was similar in all parts of the cell, no 

 longer holds true, as we observe, after these short periods of actividy, 

 a differentiation between the contents of the outer and of the inner 

 regions of the cell. E>om the inner margin of any cell to a region 

 represented by the median portion of the nucleus, the cytoplasm has 

 not changed in appearance from what we found in all parts of the 

 normal gland cell. The boundary between the two regions of cyto- 

 plasm which lies near the median line of the cell is general fairly 

 distinct, and, in many places, extends in long or short pointed pro- 

 cesses into the outer half of the cell, sometimes nearly to its outer 

 margin. In the outer half of the cell the cytoplasm is lighter in color 

 and not so dense as that we have just noticed; in this outer part 

 there are darker areas scattered irregularly near the outher margin 

 of the nucleus. Here there are also a number of fairly large vacu- 

 oles along the outer margin. These vacuoles are nearly all elongated 

 and each lies with its long axis at right angles to the surface of the 

 gland; they vary in number in different parts of the sections but we 

 were unable to distinguish that those parts where they were most 

 frequent occurred at any regular place relative to the position of the 

 nucleus. In some of the glands which had been active for this short 

 period we often noticed in the outer half a decided striation which 



