MOUTH PARTS OF THE SUBIMAGO AND IMAGO. 



places are taken by smaller less vacuolated cells. These new leucocytes grow in 

 size and soon are characteristically vacuolated (p. 355)." 



That the same cells may appear very unlike with different fixers is possible. 

 None of the authors quoted have used a technique which permits a direct com- 

 parison of plasma cells in section and in smear. 



In the metamorphosis of the muscles of May-fly mouth-parts, I find no 

 evidence of a proliferation of free tracheal cells. There is a rapid increase in 

 tracheal cells just after the various nymphal molts, but they form tracheoles. The 

 varieties of plasma cells in the vicinity of the degenerating muscles are the same 

 as those found in the first instar nymph. The muscle nuclei clearly degenerate. 

 There is no evidence of phagocytosis. 



22 



