§ 4.213 ECTODERMAL ENDOCRINE GLANDS OF ARTIIROPODA 137 



Wax 



Fig. 4-6. Experimental method used 

 to test the action of hormones in dia- 

 pausing pupae of the Cecropia silk- 

 worm, Hyalophora. The pupa in 

 front is joined, by a plastic tube up 

 to 3 cm in length, to an isolated 

 abdomen behind. The tube passes 

 at either end through a disc {Di) 

 which closes the cut surface of the 

 abdomen, being sealed in with paraf- 

 fin wax. Windows {W) can be sealed 

 in at either end for observing the 

 onset of differentiation in the internal 

 tissues. This is stimulated by im- 

 planting a chilled, and therefore 

 activated, brain into the hinder 

 abdomen {Im) ; prothoracotrophin 

 from the implant causes secretion of 

 ECDYSONE, the moult-promoting hor- 

 mone, from the prothoracic glands 

 in the front specimen {A), which 

 reacts first. Diapause is broken later 

 in the hinder abdomen when it is 

 reached by the haemolymph bearing 

 ecdysone from the front specimen 

 (based on data from Williams, re- 

 drawn after Hinton, 1951). 



been specifically investigated. Presumptive evidence in favour of 

 such an effect is that both the metaboHc and morphogenetic 

 functions of the glands are carried out simultaneously, so that they 

 could be due to the same prothoracic hormone under the same 

 endocrinokinetic control. 



