VI 



and fresh-water shells, from the comparative 

 facility with which the subjects may be collected 

 in their living state. 



How far unloosed for casualties may some- 

 times befriend the researches of the Naturalist, 

 the following circumstance will elucidate. 



A few summers since, I had collected some 

 stagnant water, for the purpose of examining 

 the infusorial tribe ; and over the head of the 

 vessel containing this water 10 as placed apiece 

 of fine gauze. Some time afterwards, upon 

 looking into the vessel, I was surprised to see the 

 surface of the water, and the under side of the 

 gauze 'strewed with minute winged insects, chiefly 

 of the Neuropterous tribe. Is it not therefore 

 probable, that the infusorial order of worms may 

 be merely the minuter species of Ephemera in 

 their mediate stages of transformation? Of the 

 natural aconomy of this last tribe we know only, 

 that the egg is dropped into water, and that it 

 emerges in a perfect winged state. The larva 

 and chrysalis metamorphosis must take place 

 under water, and for this purpose they must be 



