116 EVENINGS AT THE MICEOSCOPE. 



quisite cone or funnel, from "whieli every drop of 

 moisture is excluded, thougli the water stands around 

 at the level of the brim. A few seconds it remains 

 motionless thiis, the whole body hanging downwards, 

 suspended from the caudal coronet, 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, lite 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 por- 

 tion more or less, of the bubble of gleaming air is in- 

 haled or expired by the animal, causing a diminution 

 or increase of its volume ; and this of itself would con- 

 vince you that it is the spiracles of the animal which 

 are thus protected. 



The application of a low magnifying power, say 

 from thirty-five to fifty diameters, for we can hardly 

 use a higher magnification than this to the animal while 

 alive, will reveal a few more of the details. 



We see, then, that the extremity of the last segment 

 forms a circular disk hollowed in the centre, where it is 

 perforated 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 opposite 

 sides — -viz., on those aspects which face the next bristle 

 on either hand, — two series of not very close-set branch- 

 lets, set like the plumes of a feather, or the pinnss of a 

 fern-leaf, which give it the elegant plumose appearance 

 which the unassisted eye recognises. The bristles have 

 a granulose surface near the extremity, and terminate in 

 fine points. 



