MUSCULATURE OF CULEX PUNGENS. 279 



through the growing stage, and are the centers of new growth 

 during the process of pupation. 



Viallanes ('82) describes the destruction of the fat-body, in 

 which he finds a setting free of granules by rupture of the cell 

 membrane. These granules constitute a sphere stained by 

 carmine surrounded by a non-staining substance, and having a dis- 

 tinct outline resembling protoplasm, and are, probably, daughter- 

 cells of the adipose cells. They resemble the embryonic cellules 

 which constitute the outline of the first muscles of flight in the 

 imago. The granular spheres of Weismann, Viallanes divides 

 into two classes, the large and the small, having many or few 

 nuclei respectively. The latter may tend to the formation of a 

 fatty fluid (puree) on dissolution of the elements. The large ones 

 are hypertrophied adipose cells and include the embryonic cellules. 



In muscular destruction he speaks of a " regressive evolution " 

 and " evolution by degeneration." In the former the muscle 

 nuclei become spherical, enveloped by protoplasm and proliferate. 

 The contractile substance disappears as if nourishing the new ele- 

 ments, an area of granules resulting. In the latter the nucleoli first 

 disappear followed by a dissolution of the contractile substance. 



As already stated, Metschnikoff ('83) changed the course of 

 study in these lines by the discovery of phagocytosis. He first 

 described certain cells of the animal body as scavengers, and gave 

 to them the name " phagocytes." Since then much of the work 

 done on the problem of metamorphosis has been upon this sub- 

 ject. Metschnikoff describes muscular phagocytes which play a 

 part in the destruction of the muscles in the metamorphosis of 

 insects and tad-poles. This phagocyte has for its nucleus that of 

 a muscle fiber which becomes enlarged and surrounded by a 

 granular protoplasm, finally breaking loose from the muscle and 

 ingesting fragments of tissue. 



Following Metschnikoff, Kowalevsky ('85) took up the work. 

 He finds leucocytes, penetrating into the muscular substance 

 of Mnsca i-oinitoria a few hours after passing into the nymphal 

 stage, and, by their pseudopods, tearing the tissues and breaking 

 passages for others. After incorporating fragments the leuco- 

 cytes return to the circulation swollen with the ingested particles. 

 These, Kowalevsky believes, are the same as the granular spheres 



