142 



THE MECHANICAL FUNCTIONS. 



individual animals are often so minute as to be scarcely vi- 

 sible without the aid of the microscope. Mere size, indeed, 

 is of all the circumstances attendant on organized beings, that 

 which should least be assumed as the criterion of complica- 

 tion or refinement of structure. An object is great or small, 

 only in relation to the standard of our own limited and 

 imperfect senses; but with reference to the operations of 

 creative power, all such distinctions must vanish. There 

 is not, as far as we have the means of judging, in the colossal 

 fabric of the elephant, any structure more complicated than 

 exists in the minutest insect that crawls unheeded at our 

 feet. 



§ 5. *dcalepha. 



Floating masses of living gelatinous matter are met with 

 in every part of the ocean; often in vast numbers and of va- 

 rious forms; and having but little the appearance of belong- 

 ing to the animal kingdom. They compose the order *^ca- 



lepha, of which the Medusa 

 (Fig. 81) may be taken as the 

 type. They appear, from their 

 organization, to be raised but a 

 single step above polypi; and 

 in point of activity and loco- 

 motive powers, they rank 

 among the lowest of those Zoo- 

 phytes which are not perma- 

 nently fixed to the spot where 

 they were first developed. 

 They are almost wholly passive 

 beings, floating on the surface 

 of the sea, or remaining at a small depth below it, carried 

 to and fro by the motion of every tide and current, and 

 destined to be the unresisting prey of innumerable tribes 

 of animals which people every part of the ocean. 



The usual form of a Medusa is that of a hemisphere, with 



