breed: METAMOKPHOSIS OF THE MUSCLES OF A BEETLE, 343 



After the classical researches of Weismann ('62, '64, '66), the more 

 importaut of the earlier authors are Kiinckel d'Herculais ('72, '75), 

 Gauin ('76), and Viallaues ('81, '82). Later authors have shown that 

 the results of these papers on the histological clianges of the muscles 

 daring pupal life are not of great importance, so that they need not be 

 mentioned in detail here. The higher (cjclorraphic) and the lower 

 (orthorraphic) Diptera seem to present, together with other dilferences, 

 two distinct types of muscle degeneration, and so the papers on each 

 group are here reviewed separately. 



a. Cydorrapha. Van Eees ('84, '88) and Kowalevsky ('85, '87) both 

 find in Calliphora that the larval muscles undergo phagocytosis. The 

 leucocytes penetrate the muscle fibres, which they break up into frag- 

 ments ; these, together with the muscle nuclei, are engulfed by the 

 leucocytes and digested. The leucocytes with their inclusions are the 

 " Kornchenkugeln " of Weismann ('64). Van Rees finds that three 

 pairs of muscles in the dorsal part of the mesothorax are exempt from 

 this fate, and that they metamorphose to form the indirect wing muscles 

 of the adult. 



Lowne ('90-95) confirms the two preceding authors in regard to the 

 phagocytosis of the larval muscles, but denies the metamorphosis of the 

 three pairs of muscles of the mesothorax described by Van Rees. He 

 states that all of the imaginal muscles are newly formed in the pupa, 

 being produced from mesoderm cells which are derived from the imaginal 

 disks. 



De Bruyne ('97) practically agrees Avith Van Rees and Kowalevsky, 

 except that he finds that the leucocytes are not the active agents in 

 breaking up the muscle substance into fragments, the muscle being 

 frequently broken up before the arrival of the leucocytes. He also finds 

 that some of the nuclei of the larval muscles are not immediately de- 

 stroyed. These, collecting a portion of the sarcoplasm of the fibre about 

 themselves, act as myoblastic phagocytes, engulfing and digesting the 

 muscle fragments. He calls this " autophagocytosis," to distinguish it 

 from ordinary or leucocytic phagocytosis. 



The results of the studies of Noetzel ('98) accord with those of De 

 Bruyne in regard to the breaking up of the muscle before the arrival of 

 the leucocytes. 



Berlese ('99, -.00, :00% :01, :02, :02*) diff'ers from the above authors in 

 many essential points. He states that there is no phagocytosis, the 

 ingestion of the sarcolytes and muscle nuclei by the leucocytes being for 

 the purpose of distributing those elements to all parts of the body. The 



