WATER GRUB OF A MAY-FLY. 139 



Dissection of tlie water-grub of a May -fly (Ephemera). The back 

 is laid open, and the nerves, intestines, and respiratory apparatus 

 exhibited, a a a a n a, six clusters of short tubes, opening on both 

 sides, through whicii the cre;iture breathes: the air contained in the 

 water, passing through these, enters '.wo wind-pipes, h b b b, running 

 from head to tail, and circulates ihrough every part of the horly. The 

 eight fins, and a portion of the tsiil bristles have been omitted, to give 

 the rest of the figuie on a larger scale. 'Jhe central white lines are 

 the nerves. 



