THE ANATOMY 0¥ THE PUPA 75 



chiefly downward with reference to the outer world. A 

 sudden loud noise or a very gentle tap upon the vessel 

 containing the pupse causes those at the surface to dart 

 downwards, but as slight sounds produce no effect upon 

 them, Dr. Hurst concludes that the tremor of the surface 

 of the water and not the sound itself is recognised by them. 

 The setae on the first segment of the abdomen are probably 

 the organs by which this movement is felt. 



