THE ASCIDIA. 



39 



the body is encased, and which, like the shell of a bivalve 

 mollusk, sheaths the mantle-covered animal within. 



The Ascidia. 



On a more attentive view, we find that there are 

 two orifices, each placed upon a projecting portion of 

 the body, one at a, the other at b, of the above figure. 



