302 EVENINGS AT THE MICROSCOPE. 



■direction, but a 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 bunghole of a barrel receives and 

 embraces the tube of a funnel. The latter cavity occu- 

 pies 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, more- 

 over, 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 



