118 STUDY OF 



above it; and, I believe, invariably in her up 

 and down flights over the water. With respect 

 to their sinking gradually, it may also be re- 

 marked, that the eggs of the ephemera vulgata, 

 when dropped into a glass of water, sink to the 

 bottom with surprising speed. 



The coats of these eggs being entirely mem- 

 branaceous, and containing no calcareous matter 

 whatever ; and the interior fluid being perfectly 

 transparent, we are the more surprised that this 

 should be the case ; but the uncommon weight 

 of the eggs is no doubt intended to enable the 

 female to select, even in rapid streams, a proper 

 resting place for her infant progeny. A similar 

 provision will most likely be found to extend to 

 all those insects which are born in water, but 

 which, in a perfect state, cannot safely come in 

 contact with it for the purpose of depositing 

 their eggs. 



Swammerdam supposed the ephemerae to live 

 three years, at least, in the water, in a larva 

 state ; scientific anglers have, however, long been 

 satisfied, that the eggs of one year become per- 

 fect insects the next. 



This acute observer did not fail to remark, that 

 the femur and tibia (especially of the posterior 



