2io FLASHLIGHTS ON NATURE 



and unprotected bodies they would almost inevit- 

 ably be frozen to death if they remained in the 

 open. On the bottom of the pond, however, they 

 huddle close and keep one another warm, so that 

 portions of the mud in the centre of the pool 

 consist almost of a living mass of frogs and other 

 drowsy animals. 



Some of the larger pond-dwellers thus hibernate 

 in their own persons ; others, which are annuals, 

 so to speak, die off themselves at the approach 

 of winter, and leave only their eggs to vouch for 

 them and to continue the race on the return of 

 summer. A few beetles and other insects split 

 the difference by hibernating in the pupa or chry- 

 salis condition, when they would have to sleep 

 in any case, and emerging as full-fledged winged 

 forms at the end of the winter. But on the whole 

 the commonest way is for the plant or animal 

 itself in its adult shape to lurk in the warm mud 

 of the bottom during the cold season. 



In No. i we have an excellent illustration of this 

 most frequent type, in the person of the beautiful 

 pointed pond-snail, a common fresh-water mol- 

 lusk, with a shell so daintily pretty that if it did 

 not abound we would prize it for its delicate 

 transparent amber hue and its graceful tapering 

 form, resembling that of the loveliest exotics. This 

 pond-snail, though it lives in the water, is an air- 

 breather, and therefore it hangs habitually on the 

 surface of the pool, opening its lung-sac every now 

 and then to take in a fresh gulp of air, and looking 

 oddly upside down as it floats, shell downward, 



