COMPOUND FORMS. 41 



tents of the air-bladder ; nor is it possible, even by the applica- 

 tion of pressure, to force out the contents, excepting by bursting 

 the bladder itself, and producing an explosion. And that the 

 animal has not the power of descending in the water, at pleasure, 

 seems to be proved by the fact that numbers of them are some- 

 times found on the shore, thrown up by the violence of the wayes. 

 Professor Owen mentions that he has seen a whole fleet of them 

 wrecked on the coast of Cornwall, to which iron-bound region they 

 had been buoyed by their air-bladders. 



Naturalists have been sadly puzzled what to make of another 

 section of these animals, known as the Diphydce, or Jelly-fish of 

 a double form. They are diminutive little creatures, and com- 

 posed of two pieces which easily separate, and when detached, 

 will swim about independently for hours together. Hence arose 

 the difficulty whether to regard these compound bodies as two 

 animals united into one, or as one animal which, for a time, 

 might be separated into two. Cuvier, and most zoologists 

 following him, adopted the former opinion, regarding the two 

 pieces as two independent animals. It has lately been very 

 satisfactorily shown, however, that the two pieces do, after all, 

 constitute but one animal, although our knowledge of these sin- 

 gular creatures is still very incomplete. Considerable diversity 

 of form prevails amongst them, and frequently, also, between 

 the two portions of the same animal. They are so beautifully 

 transparent as to be almost invisible in the water, and occur 

 chiefly at great distances from the shore in the seas of warm 

 climates, where they abound in great profusion. 



Nothing connected with the Jelly-fish more truly deserves to 

 be characterized as wonderful than what has of late years been 

 discovered with respect to their mode of reproduction. Two 

 distinct modes of increase have been ascertained to prevail 

 amongst these animals one by the development of eggs, the 

 other by the process of budding, or gemmation. According to 

 the latter mode, which was first observed by Sars, a Swedish 

 naturalist and clergyman, the young Jelly-fish sprout from the 

 bodies of their parents like the leaf-buds of a plant, and after 

 attaining to a certain stage of advancement, become detached, 

 and swim away, to enjoy a free and independent existence. 



The singularity of this mode of increase is apt to be under 

 rated, because of the insignificance of the creatures amongst 



