FORMATION OF THE IMAGO OF MUSCIDAE 



673 



which the parts of the head of the fly are developed in close rela- 

 tion to those of the larva, and the types in which deep invaginations 

 lead apparently to the formation of similar new parts far within 

 the body, the seeming independence of the new parts being in- 

 tensified by thoroughgoing histolysis," and they suggest that possi- 

 bly types may be discovered intermediate between Chironomus and 

 Muscidae. 



We are now prepared to consider the extremely complicated 

 changes, in the Muscidae, leaving out of consideration the origin of 

 the wings from imaginal 

 buds, which has already 

 been discussed on pp. 

 126-137. 



Formation of the imago 

 in Muscidae. 1 - - In the 

 flesh, and undoubtedly 

 the house, and allied flies 

 the germs or imaginal 

 buds of the legs and 

 wings arise in the same 

 way as in Corethra. But 

 in the Muscidse, the buds 

 are situated far within the 

 interior of the body, the 

 peripodal cavities appeal- 

 closed, and the peripodal 

 membrane stands in con- 

 nection With the hypo- Fi. 626. A, B, C, />, diagrams of transverse sections 



showing the development of the wings, legs, and the imagi- 



derilllS merely by means nal bypodemns of muscki flies from the imaginal buds of the 



, ,. , i 1-1 larva during metamorphosis: ///, ehitinous integument of 



Of a delicate thread-like larva from which the underlying hypodermis (thy) has with- 



,, ,, . drawn; lid, imaginal buds of wings, tin, of legs ; in, the 



StalK. IniS Connecting cords connecting them with the "hypodermis ; j, wing- 



i 1 ' 1 , 4- I germs; b, leg-germs ; iJiy, imaginal hypodermis spreading 



COrCl, WHICH was nrSL lie- ou t \\\ D from the imaginal buds. The imaginal rudiments 



-i 1 TN -I of the hypodermis are indicated by thick, black outlines, the 



Dy 'eWltZ, ana larval hypodermis by two thin, parallel lines. After Lang. 



whose interpretation was 



entirely right, shows in its interior, as Van Rees proved, a narrow 



cavity. 



Though the earliest stages in the development of imaginal buds 

 in the embryo of the Muscidae are still unknown, yet we shall not 

 go far astray if we refer them, like the imaginal buds of Corethra, 

 to hypodermal invaginations. We must, then, regard the stalk-like 



1 This account is translated from Korschelt and Heider, with some omissions and 

 slight changes. 



2x 



iluj 



