124 EVENINGS AT THE MICROSCOPE. 



interrupted at its middle point ; and just there, in each 

 pro-leg, a clear vesicle or fleshy bladder protrudes from 

 the sole, which may perhaps serve as a very delicate organ 

 of touch, or may exude a viscid secretion helpful to pro- 

 gress on smooth bodies. The hooks seem adapted to 

 catch and hold the fine threads of silk, which most cater- 

 pillars spin as a carpet for their steps. 



In some cases the circle of hooks is complete, as in this 

 example, which I find in one of the slides of my drawer, 

 marked " Pro-leg of a Caterpillar." It is some large 

 species, probably a Sphinx, for the hooks are very large, 

 of a clear orange-brown hue, and set in a long oval ring — 

 single as to their basis, but double as to their points — 

 completely around the extremity of the foot. These hooks 

 belong only to the skin, as may be well seen in this pre- 

 pared specimen — doubtless mounted in Canada balsam ; — 

 for their roots are mere blunt points, set but little below 

 the surface of the thin skin without any enlargement or 

 apparent bulb. 



