52 AQUATIC MICROSCOPY *'0R BEGINNERS. 



came filled with air or gas at flowering-time, and so 

 lifted the flower-stalk and the blossoms above the 

 water. This was interesting, but the truth is more 

 interesting and startling. The plant actually feeds on 

 animals. These bladder-like bodies are the food-traps, 

 they are the mouths and the stomachs of Utricularia. 



Under the microscope the utricles are seen to be hol- 

 low, ovoid bodies, with a narrow, almost straight an- 

 'terior end, and with several long bristles projecting 

 forward or away from the body of the utricle, these 

 bristles probably serving as a guide to an opening at 

 their base. A little animal swims against a bristle, 

 and naturally moves down it towards the opening at 

 the mouth of the utricle, which it finds closed by a 

 transparent colorless curtain; this it pushes aside and 

 passes on into the trap. The curtain-like valve is at- 

 tached by its upper and lateral margins, therefore 

 hanging before the opening in the utricle, and swing- 

 ing inward, but so arranged that it cannot be forced 

 outward by any creature small enough to pass within. 

 Indeed the power that the valve seems to exert is as- 

 tonishing. Small fish have been found with the tail 

 or even with the head inside the utricle, arid firmly- 

 held by the pressure of the valve. In these cases, 

 hojvever, it seems probable that the struggles of the 

 dying fish may have wedged it fast, rather than that 

 the valve has held it. 



Small worms and worm-like larv-se have been found 

 half in and half out of these fatal traps, for once past 

 the curtain-like valve the little animal never escapes. 

 And no sooner has it entered than it begins to show 

 signs of discomfort; if it has a shell it- withdraws its 

 legs and head and . closes the shell; if a worm or 



