806" EVENINGS AT THE MICROSCOPE. 



When the disk has grown to such an extent as to spread 

 over ahout half of the larval stomach, very little remains 

 of the helmet, except the middle portions of the glassy 

 rods and the ciliary bands ; all the rest of this exquisitely 

 modelled framework having vanished by insensible degrees, 

 no one knows how or where. The stomach and gullet, 

 indeed, are gradually sucked into the ever-growing disk ! 

 but all the rest, flesh and rods, fringes, bands, and cilia, 

 waste away to nothing. 



The mouth of the larva has no connexion with the 

 mouth of the Urchin. The little isolated patches of glassy 

 network continue to spread through the flesh of the disk, 

 until the whole forms one uniform structure, and con- 

 stitutes a series of plates. The mouth is that spot in the 

 centre, over which the calcareous frame is last extended ; 

 and it is first distinguishable by the appearance of five 

 glassy points, which soon develop themselves into the five 

 converging jaws, which we see forming such a curious 

 apparatus on the inferior side of the Sea-Urchin. 



Actual observation has not traced the infant animal 

 beyond this stage of the development ; but Professor 

 Miiller has taken specimens, swimming in the sea, in 

 which scarcely a rudiment of the larva remained. They 

 had the form of round flattened disks, which freely moved 

 their spines, and crawled about the sides of the vessel in 

 which they were kept by means of their suckers, exactly in 

 the manner of the adult Urchin. 



" Thus ends this strange, eventful history ; " and in 

 reviewing it, one can scarcely avoid being impressed with 

 a sense of the majesty of God in these His humbler works. 

 By what wonderful, what unexpected roads does He arrive 

 at the completion of His designs ! and if such things as 

 these are only now bursting upon our knowledge, after 

 thousands of years of man's familiar contact with the 

 inferior creatures, how many more wonders may yet 

 remain to be unfolded, as science pursues her investiga- 

 tions into the Divine handiwork ! 



