220 STRUCTURE OP MEDUSA. 



ingly simple, but not the less wonderful on that account. 

 Our wonder is, indeed, the more excited when we find 

 creatures of large size, as many of the Medusae are, 

 and endowed with considerable powers of perception, 

 and some strength and agility, formed of a few delicate 

 tissues filled with a fluid, to all appearance, not very 

 different from sea- water. It is as if we had to investigate 

 the structure of submarine bubbles. Take one of the 

 largest of the race, weighing many pounds while living, 

 and dry it. The whole contents of the body will either 

 leak away or evaporate, and nothing will be left but 

 some small shreds of membranous skin, forming a glis- 

 tering stain on the surface of whatever object the Jelly- 

 fish was placed upon. The flesh is entirely composed of 

 large cells of delicate structure, filled with a transparent 

 fluid. But these cells are put together with the most 

 rigid accuracy, and their arrangement is so varied that 

 naturalists have had to distinguish numerous families 

 and genera of Jelly-fishes. The number four prevails 

 through the whole class. All the parts of the body are 

 divisible by four, and mostly ranged in a radiate manner 

 round a centre, so that either the animal is cruciform, 

 or its internal parts are so arranged. But this form, 

 though very general, is not universal : some resemble 

 long ribbons ; others are oval or irregularly curved. 



The Jelly-fishes have been classed according to dif- 

 ferences in their locomotive organs. Our most common 

 species, referable to the Linnsean genus Medusa (but 

 now comprising several distinct genera, according to 

 the views of modern naturalists), are distinguished by 

 an umbrella-shaped body, generally pellucid, from the 



