DEVELOPMENT 
179 
condition. In accounting for the evolution of metamorpho- 
sis, the theory of natural selection 
finds one of its most. important appli- 
cations. 
3. INTERNAL METAMORPHOSES 
In Heterometabola, the internal 
post-embryonic changes are as di- 
Rect, as, the external changes. of 
form; in Holometabola, on the con- 
trary, not all the larval organs 
pass directly into imaginal organs, 
for certain larval tissues are de- 
molished and their substance recon- 
structed into imaginal tissues. When 
Fic. 220. 
Ww 
Diagrammatic transverse sections of muscid larve, 
val hypodermis; i, larval integument; if, imaginal 
leg; w, imaginal bud of wing.—Modified from Lang’ 
FIG. -210. 
a mS 
Diagrammatic transverse 
section of Corethra larva, to 
show imaginal buds of wings 
(w) and legs (/); h, hypoder- 
mis; i, integument.—Modified 
from Lang’s Lehrbuch. 
to show imaginal buds. h, lar- 
hypodermis; 7, imaginal bud of 
s Lehrbuch. 
