CHAPTER III. 



On the Larva and Crysalis* of a Day Fly. 

 Ephemera marginata of Stephens. 



WHEN this larva issues from the egg, which it does in 

 the decline of summer, it has at intervals an unsteady 

 motion in a manner, as it would seem, involuntary. 

 During this stage it is scarcely visible to the unassisted 

 eye, and is very pellucid. As it increases in size, the 

 serpentine vessels attached to the sides of the animal 

 become more apparent, and the tail assumes that rich 

 feathered appearance, which, in conjunction with the 

 paddles, form its pre-eminent beauty. 



While the insect is very young, it is a well-suited 

 object for the solar achromatic microscope, in which it 

 will afford an ample fund of amusement, when repre- 

 sented on a screen, and dilated to the extent of about 

 two feet in length. If the instrument be truly aplanatic, 

 every part of the insect's internal organization may be 

 clearly seen; and the peristaltic motion of the intes- 

 tines, the circulation of the blood, and the pulsation of 

 the dorsal vessel, can be observed without the least 

 'rouble, by any number of persons. In the latter circum- 

 stance the principal advantage of this instrument con- 



* It may, perhaps, be termed either, according to its state of growth. 



