in the Fish Gallery of the Indian Museum. 5 



of which are shown in Case 3, there is a tail for loco- 

 motion. 



As the Ttmicata of these seas have never been named, 

 our exhibits are chiefly intended to illustrate some of 

 the more important anatomical modifications of this 

 most interesting group of animals. 



The structure of the typical adult Ascidian is shown 

 in the series of drawings, dissections and enlarged 

 models in Cases 2 and 3. 



The vertebrate affinities of the Ascidian larva are 

 represented by a series of enlarged drawings, chiefly 

 after Ray Lankester, in Case 3. 



1. THE TTPICAL SIMPLE FIXED ASCIDIAN. 



[Case 2.] 



Nos. I and I in this Case are simple fixed Ascidians 

 preserved in spirit. Observe the form and orientation 

 of the body, the incurrent opening, or mouth, and the 

 excurrent or atrial opening, shown by labels. 



Nos. II and III are simple fixed Ascidians in which 

 the whole of the right side of the test has been removed. 

 Observe the animal lying completely enveloped in its 

 mantle, which is the outer layer of the body wall ; 

 thus enveloped it appears to hang almost free within 

 the test. Notice also the siphons, or processes of the 

 mantle which open at the mouth and at the atrial 

 orifice. 



Nos. IV. V. VI. are simple fixed Ascidians of which 

 the left side of the tunic has been removed, and more 

 or less of the left side of the mantle also. We now see 

 that beneath the mantle there is a space. This space 

 is the atrial or peribranchial cavity : it opens directly to 

 the exterior by the atrial or excurrent orifice of the test 

 only. The pointer in No. V shows the passage from the 



