WHEEL-BEARERS. 



201 



males of all the species have a very close similarity to each 

 other. 



The females produce and deposit, one at a time, very 

 large oval eggs, enclosed in a brittle shell. The young 

 appear in the perfect form, being subject to no metamor- 

 phosis, and for the most part with all their organs com- 

 plete. In some of the lower forms, as Stephanoceros, Me- 

 licerta, &c, the young are hatched in a grub-like condi- 

 tion, from which the tentacles, disk, &c, develop them- 

 selves by gemmation. 



The genera just alluded to, and some others, are inca- 

 pable of locomotion, except in earliest infancy ; the young 

 soon attaching themselves by the foot to some solid object. 

 They now secrete and throw off from the surface of their 

 body successive coats of gelatinous matter, which form an 

 erect cylindrical case around them, into which they can 

 wholly retire for protection, by contracting their fore parts 

 on alarm. In general, this tube is simply gelatinous 

 and transparent, except that it sometimes becomes par- 

 tially opaque when old, by the adhesion to its exterior 

 of Diatomacece, floccose particles, &c. ; but in one species 

 (Melicerta ringens), which hence becomes invested with a 

 high interest, the tubular case is strengthened by a layer 

 of solid pellets, manufactured by the animal for the occa- 

 sion, and deposited, pellet by pellet, and layer upon layer, 

 just like the bricks in a piece of masonry. 



This species is one of peculiar beauty, and any of our 

 young readers who possess a microscope, or have access to 

 one, will do well to obtain an hour's examination of it. 

 Fortunately, it is by no means a rare animal in still waters 

 where aquatic plants grow: the slender, much divided 



