302 EVENINGS AT THE MICROSCOPE. 



little diverging ; and two other shorter rods pass down 

 from the front of the ring, parallel to these. After a while 

 each lateral pair of rods is united by a short cross-piece, 

 and the result is four lengthened rods, two of which go 

 down through the vizor into the chin-points, and two 

 larger and stouter ones through the ears into the shoulder- 

 points. This, then, is the solid skeleton, the interest of 

 which is much enhanced, when we observe that it is 

 formed, on the common plan, out of perforated lime-glass, 

 the two ear-rods and the crest-rod being pierced with a 

 regular series of oval holes, and bearing on their edges 

 corresponding projecting points. 



Now, to turn again to the gelatinous flesh. The inner 

 surface of the vizor, or that which would be in contact 

 with the face of the wearer, supposing it to be a real 

 helmet, has a great squarish orifice with a thickened 

 margin, which we see by its movements to be highly sen- 

 sitive and contractile. This square orifice is the mouth of 

 the larva, and it leads into a cavity in the upper part of 

 the vizor, which is the gullet ; and this in its turn ter- 

 minates in a narrowed extremity, which passes into the 

 orifice of a greater and higher cavity, the lip of which 

 embraces it just as the bung-hole of a barrel receives and 

 embraces the tube of a funnel. The latter cavity occupies 

 the chief part of the volume of the helmet, the four rods 

 diverging to inclose it. It is the stomach. 



It adds to the beauty of the little helmet-shaped crea- 

 ture, that while the greater portion of the substance is of 

 the most colourless transparency, the summit of the crest 

 and the tips of the shoulder-points are tinged with a lovely 

 rose red. The whole exterior surface is, moreover, studded 

 with those minute and glandular specks, with which every 

 part of the adult Urchin is covered; and the light is 

 reflected from the various prominences with sparkling 

 brilliancy. 



The little creature moves through the water with much 



