102 



EVENINGS AT THE MICROSCOPE. 



then suddenly the tips of the plumes curve inward toward 

 each other, inclosing a globule of air, and the animal 

 wriggles away into the depths, carrying its burden, like a 

 pearl, or a glittering bubble of quicksilver, behind it. 



This you may observe with the unassisted sight ; and 

 you may mark also, how, from time to time, a portion, 

 more or less, of the bubble of gleaming air is inhaled or 

 expired by the animal, causing a diminution or increase 

 of its volume ; and this of itself would convince you that 

 it is the spiracles of the animal which are thus pro- 

 tected. 



The application of a 

 low magnifying power, 

 say from thirty-five to 

 fifty diameters, for we 

 can hardly use a higher 

 power than this to the 

 animal while alive, will 

 reveal a few more of the 

 details. 



"We see, then, that the 

 extremity of the last seg- 

 ment forms a circular 

 disk, hollowed in the 

 centre, where it is per- 

 forated with the two 

 orifices of the air-pipes. 

 The margin of this disk 

 carries about thirty stiff 

 but slender spines or 

 bristles, some of which 

 are branched in a forked 

 manner. Each bristle 

 bears, on its two oppo- 

 site sides — viz., on those 

 aspects which face the next bristle on either hand— two 



GRUB OF CHAMELEON-FLY. 



