469 



AU figures are from sections of L. decem-Uneata, and were drawn with a Abbe 

 Camera, from materiul killed in Acetic Sublimate and stained with Mayer's 

 Haemalum. 

 Fig. 1. Transverse section of the pronotum of a pro-pupa just before the final 



transformation, showing the closely packed, and highly vacuolated 



exuvial cells. Bausch &• Lomb -/s in. obj., 2 in. oc. 160 mm. 

 Fig. 2. Exuvial cell in process of degeneration. Bausch & Lomb Vs in- obj., 1 in. 



oc, 160 mm. 

 Fig. 3. Exuvial cell in the most extended condition pouring out its contents be- 

 tween the old and freshly forming cuticula. Bausch &- I>omb i/o in. 



obj., 1 in. oc, 160 mm. 

 Fig. 4. Exuvial cell in stage of degeneration. Bausch &• Lomb '/r, in. obj., 1 in. oc, 



1 70 mm. 

 Fig. 5. Exuvial gland in a late stage of degeneration, just before being attacked 



by phagocytes. Biusch & Lomb i/n in. obj., 1 in. oc, 170 mm. 

 Fig. G. Exuvial or seligerous cell in larvae of third instar. Bausch 6c Lomb i/s in. 



obj , 1 in. oc, 160 mm. 

 Fig. 7. Setigerous cell in the third larval stage just before ecdysis, showing a stage 



intheformationof anewhair. Bau?ehiS: Lomb Vs^n- ol^j-j 1 in- oc, 165 mm. 

 Fig. S. Section of the body wall showing separation of the old cuticula from the 



hypodermis by the exuvial fluid in the pro-pupal stage. B.iusch cV Lomb 



If, in. obj., 2 in. oc, 160 mm. 



by which they are seen to be pouring out their contents (Fig. 8) 

 between the oLl and the rapidly forming new layer of cuticula. They 

 are most abundant along the anterior edge of the pronotum, Avhere 

 they are often thickly crowded together (Fig. 1), but they are also 

 found scattered irregularly over the body surface, being quite abundant 

 about the base of the legs. In sections made through a larva about to 

 pupate these cells (Fig. 1 are found to be well developed and distended 

 with a secretion (Figs. 1 and 3). Soon, however, their contents are 

 extruded between the old cuticula and the hypodermis, forming a 

 thin layer between them. The hypodermal cells are now perfectly 

 naked and no trace of the new cuticula can be found (Fig. 4). 



At this time these cells are large with a deeply staining nucleus 

 and two dense nucleoli. They connect with the exterior by a more or 

 less blunt process which may open in a small pore (Fig. 3) or in a 

 large rupture in one side of the cell. The cell wall is relatively thin, 

 but perfectly distinct, and shows no modifications of any kind. The 

 Cytoplasm is composed of a watery albuminous material in the form 

 of globules surrounded by the denser ]ilasma. The vacuoles found in 

 preparations are probably in life filled with a fluid which is extracted 

 in preparation, for they remain unstained by anything I have used. 

 Only in rare cases have I found a faint staining of the contents of 

 these vacuoles. The plasma is finely granular and shows no characters 

 of interest. The nucleus of these cells is large, round or oval in shape, 

 and often branching more or less (Fig. 3) in fine dendritic processes 

 between the chylema globules of tlie cytoplasm. Tiie nuclear mem- 



