214 EVENINGS AT THE MICROSCOPE 



the terminal one; its extremity is forked, and the external 

 angles are long, slender, pointed, and attached to the last 

 annulation by joints. Between the external angles, and on 

 each side of the median line, are three lesser spines, also 

 attached to the last ring by joints. Between the eyes, and 

 from near the edge of the shield, hangs a long, stout, and 

 somewhat compressed appendage, which, as the animal 

 moves, is reflexed posteriorly between the claws. Under 

 each eye is another appendage, shorter, and slightly more 

 compressed. The claws are in three pairs; each is com- 

 posed of three joints, and terminates in four long, slender, 

 hair-like appendages. These claws are generally bent on 

 the body, but stand in relief from it. If the animal be 

 viewed in front, the lower margin of the dorsal shield will 

 be found to be waved into three semicircular festoons, the 

 two external of which are occupied by the eyes, and be- 

 tween which the middle one intervenes ; the general direc- 

 tion of the claws will be seen to be at right angles to the 

 body. As the young lies enclosed within the membranes 

 of the egg, the claws are folded on each other, and the tail 

 is flexed on them so far as the margin of the shield, and, 

 if long enough, is reflexed over the front of the shield be- 

 tween the eyes. The dorsal spine is bent backward, and 

 lies in contact with the dorsal shield ; for the young, when 

 it escapes from the egg, is quite soft, but it rapidly hard- 

 ens and solidifies by the deposition of calcareous matter 

 in what may be called its skin. The progress of this so- 

 lidification may be very beautifully observed by watching 

 the circulation in the dorsal spine. When the creature has 

 just effected its liberation from the egg, the blood -globules 

 may be seen ascending to the apex; but as the consoli- 

 dation advances, the circulation becomes more and more 



