Cytological studies on the spinning glands of Platyphylax etc. 409 



very distinct, in others not so clearly defined. The vacuoles are in 

 most instances elongated and arranged at right angles to the surface 

 of the gland, the greatest number being nearest its outer surface, al- 

 though a few extend invi^ard nearly to the nucleus. The darker colo- 

 red cytoplasm of this region is in small, somewhat elongated masses, 

 most of which run parallel to the vacuoles, which lie between them. 

 An exception to this general arrangement was found in a couple of 

 specimens in which the darker areas of the cytoplasm were present 

 as in the others, and were also noticed along the inner margin of 

 the nucleus. 



In the nucleus no marked changes have taken place except in 

 the outline of its membrane, which has become more irregular, and 

 in some specimens shows along its outer margin a number of lobate 

 or pointed processes. Korschelt [9] always figures these processes 

 along the inner margin, that toward the lumen of the gland, whereas 

 in Platyphylax they are on the outer margin. The nucléoles were 

 somewhat more irregular in outline, this being in some specimens 

 decidedly more pronounced than in others. Some of the nucléoles 

 contained vacuoles. 



Glands from larvae which have been active forty -eight hours 

 show but little change from those we have just described and but 

 slight mention need be made of them. In surface view the nucléoles 

 more frequently show a linear arrangement, especially in the narrower 

 parts of the nucleus. 



After seventy-two liours of activity (Fig. 16) we find the inner 

 part of the gland still composed of cytoplasm which is of an even 

 structure, similar to the other periods of activity we have described. 

 It differs, however, frem the others in that this even part is narrower 

 and is sometimes broken by the striations which have heretofore been 

 exclusively present in the outer half or two-thirds of the cell. The 

 striae are, in some parts of the sections, seen to curve towards the 

 middle of the inner surface of the nucleus and in this region small, 

 denser areas are noticeable. This inner layer is narrower than hereto- 

 fore and restricted to one-fourth or one-third the thickness of the cell. 

 With the decrease in extent of this evenly granular part of the cyto- 



