206 POPULAR HISTORY OF THE AQUARIUil. 



exposing them to the air in a dry state for twenty-five 

 minuteSj he found that all had perished/^ 



Whatever may be thought as to the conclusiveness of these 

 experiments^ it seems certain that the power of the insects 

 to resist cold is greater than that which enables them to 

 resist drought. Miiller '^exposed some individuals in a 

 glass vessel to a freezing air, and, when fully frozen, he con- 

 tinued the exposure for twenty-four hours. At the end of 

 that time he placed the vessel containing their bodies in a 

 warm bath, watching the effect of this upon them frequently 

 during the succeeding twenty-four hours, but without seeing 

 any motion. Next morning however upon looking into the 

 vessel he observed, not without wonder, the insects alive, 

 and swimming about as before congelation, the females with 

 their bags of eggs adhering to them as usual.''^ 



The Lerneada are a parasitical family, which by various 

 meaus attach themselves to fish upon which they prey. In 

 some cases this is done by means of the foot-jaws, which 

 are strong and hooked. " In others it is by means of two 

 long appendages springing from the upper part of the 

 thorax, one on each side, and uniting at the tip, forming 

 at their junction a sort of round button. In a third set 

 again the organs of attachment are a series of horns or ap- 

 pendages proceeding from the sides of the head.''' 



