ECHINODERMATA. 59 



pins, are cut along their meeting edges, into minute 

 teeth, which fit and lock into each other with ex- 

 quisite precision. The whole body and head are 

 invested with a gelatinous flesh, in which are im- 

 bedded minute red glands, that are common to 

 the integument of the whole Class, and this is 

 covered with a series of vibratile cilia. 



What may be the use of these very curious organs 

 in the economy of the animal, is as yet unknown. 

 Their prehensile power is obvious ; but whether 

 this is exercised in the way of defensive weapons, 

 or as hands to catch food and pass it to the mouth, 

 is among the things that we have yet to learn. 



All the Echixodermata pass through a sort 

 of metamorphosis, not less wonderful than other 

 passages of their history. Until lately we knew 

 nothing of the early life of these animals ; but 

 Johann Muller has, with great skill, industry, and 

 success, solved this problem. The first condition 

 of every Echinoderm is the same; an egg-like 

 body, covered with cilia, resembling an Infusorium. 

 Changes take place, and we presently see another 

 form assumed, which varies in some degree in the 

 different families. I lately had the pleasure of 

 finding in my dip-net several little larvse of an 

 Ojpliiocoma; and the aspect of one of these may 

 serve to illustrate the subject. 



A painter's long easel affords the only object 

 with which to compare the little creature ; for it 

 consists of four long, slender, calcareous rods, 

 arranged two in front and two behind, with con- 

 necting pieces going across in a peculiar manner, 

 and meeting at the top in a slender head. 



On this shelly, fragile, and most delicate frame- 

 work, as on a skeleton, are placed the soft parts of 



