1 66 



METAMORPHOSIS 



growth as they are liberated, and so the new creature is formed, 

 the process of growth in certain parts going on while destruc- 

 tion is being accomplished in others. Considerable discrepancy 

 prevails as to the extent to which the disintegration of some 

 of the tissues is carried. 



According to Kowalevsky ^ it would appear that after the 

 phagocytes have become loaded with granules they serve as 

 nutriment for the growing tissues, and he thinks they become 



blood-cells in the 



The process of histolysis has been 



Fig. 87. Imaginal discs of Muscidae in process of development : A, Brain and 

 ventral ganglion of a larva 7 mm. long of M. vomitoria ; v, ventral ganglion ; 

 c, cephalic ganglion ; h, head nidiment ; vc, portion of ventral chain ; pd, 

 prothoracic rudiment ; vc^, third nerve ; md, mesothoracic rudiment : B, meso- 

 thoracic rudiment, more advanced, in a pupa just formed of Sarcophaga carnaria, 

 showing the base of the sternum and folds of the forming leg, the central part (/) 

 representing the foot : C, the rudimentary leg of the same more advanced ;/, femur ; 

 t, tibia ; /j, f^, tarsal joints : D, two discs from a larva 20 mm. long of Sarcophaga, 

 attached to tracheae ; msw, mesonotal and wing-rudiment ; mt, metathoracic rudi- 

 ment : E, r, mesothoracic rudiment of a 7 mm. long larva attached to a tracheal 

 twig. (After Weismann and Graber. ) 



chiefly studied in the blowfly, and not much is known of it in 

 other Insects, yet it occurs to a considerable extent, according to 

 Bugnion^ and others, in the metamorphosis of Lepidoptera. 

 Indeed it would almost seem that the processes of histolysis 

 and histogenesis may be looked on as exaggerated forms of the 

 phenomena of the ordinary life of tissues, due to greater rapidity 

 and discontinuity of tissue nutrition. 



1 Zool. Anz. viii. 1885, p. 125. 



2 Mitt, Schtveiz. ent. Ges. viii. 1893, p. 403. 



Jl 



