MOUTH PARTS OF THE SUBIMAGO AND IMAGO. 



pink in color, and the cell contents (II), begin to liquify. The nuclei (n) assume 

 a spherical shape and their chromatin becomes diffuse. Plasma cells of the five 

 varieties (A, B, C, D, E) increase in the proximity of the degenerating muscle. 

 In cross section (IV) Cohnheim's areas are not evident, and many of the fibers 

 are vacuolated. As degeneration increases, the dark bands disappear (III) and 

 the muscle substance stains more and more faintly. The sarcolemma is no longer 

 evident, and the nuclei (n) rupture. Finally nothing remains but a formless 

 mass (V), and that soon ceases to stain. There is no evidence of phagocytosis. 

 During the muscle degeneration no plasma cells are present that do not 

 occur in a first instar nymph. The following differential count from smears of 

 the plasma of nymph, subimago and imago shows a proportional increase in 

 varieties D and E after transformation, and a decrease in varieties A and B. 



* % of Plasma Cells in Differential Count. 



Tracheae (PI. VI, fig. 86, Tr.) and tracheoles (tr) persist after the muscles 

 have entirely lost their identity. These cells have a finely granular dark purple 

 staining cytoplasm, and a densely staining finely reticular nucleus. 



DISCUSSION. 



The nature of the cells present in the vicinity of metamorphosing muscles 

 among holometabolic insects has long been a subject of discussion. Berlese and 

 Terre contend that the cells are not leucocytes, but are developed from the nuclei 

 o>f the larval muscles; Anglas and Perez, that they do not arise from the nuclei 

 of larva! muscles, but are leucocytes. Deegner says that spindle-shaped cells 

 whose origin is uncertain, appear in the late larva of Hydrophilus. Breed, 1913, 

 in a very complete work on the metamorphosis of the muscles of a beetle writes : 

 "Mesenchymal cells arise singly from the tracheae or hypodermis, and give rise 

 to tracheae, leucocytes, and other related tissues (p. 353) — It is probable that 

 some of these tracheal cells become leucocytes — Certainly the large vacuolated 

 leucocytes which have persisted from the larva, disappear in old pupae, and their 



*100% = 500 plasma cells. 



21 



