THE LIFE CYCLE 



35i 



Not all of the body is thus destroyed, however; there are 



preserved little islands o 

 regenerative cells in all the 

 principal parts of the body 

 from which their respective 

 continents will be reformed. 

 In the walls of the stomach, 

 for example, there are grouped 

 rings or masses of little cells, 

 rich in protoplasm, by which 

 the new epithelium of the new 

 stomach will be developed. 

 The undeveloped legs and 

 wings exist in the larva as 

 little buds of active cells, at- 

 tached to the inner face of the 

 body walls. From these legs 

 and wings now grow out, at 

 first beneath the larval skin, to 

 be freed at its last moulting. 

 About the bases of these 

 organs and from other regen- 



FiG. 203. Cone galls of 'the willows f^rufUrn ppH maccpc in +V.e -ixroll 

 caused bv the gall midge Rhabdophaga eraXlVC CCU maSSCS m tHC Wall 



y/od'S^Sn ^SaiL^^di^c^o^Srl. fhe itsclf, the new body wall is 

 bebtiana.^""^ ^^^^ produced on Saiix developed. Details of thcse 



wonderful processes may not 

 be studied here, but there are some easily observable phe- 

 nomena, which will help us to understand the main points. 



Study 42. Observations on internal metamorphosis. 



Materials ne<^^ed: Living larvae and pupae of some 

 dipterous species having red blood* ; preferably of the cone 



*The blood of insects is not red, except in a few forms, such as 

 the so-called "blood worms", that are the larvae of midges (Chir- 

 on omidae), and in some of the larvae of gall midges (Cecido- 

 myidae). 



