TUNICATA. 5 



tliemselves ; . . . but after more than half an hour's atten- 

 tion, the vessel lying very quiet all the time, I did not per- 

 ceive the least appearance of any of these polypes; upon 

 which I brought them to the shore in sea- water, and then, 

 by means of my microscope, I discovered every one of those 

 stars to be a true animal, and much more beautiful than any 

 polype, but quite of a different structure, which I shall now 

 describe/' Then follows a description of the " little radiat- 

 ing bodies, witli their contracting and expanding mouths, 

 and the little tender fibres moving at the bottom." And 

 then the writer proceeds : " By comparing and examining all 

 the various pieces I had collected of this fleshy substance, 

 with its shining stars, I observed that the size and colour, 

 as well as the very figure of the stars, varied greatly ; but 

 the structure of the leaf-like radii, and that of their mouths 

 and their motions, were perfectly the same in every indi- 

 vidual." 



The simple Ascidians, or " leather-bag'' Tunicata, are 

 more independent and unsocial in their way of living. The 

 rudely-formed case, clinging to the weed or rock, and some- 

 times encrusted, with stones, shells, and corallines, is found 

 to compose the outer covering of a single animal, whose 

 principal duty in life appears to be that of sitting still with 



