in the Fish Gallery of the Indian Museum. 7 



that enter the branchial sack with the water of respira- 

 tion find their way into the gullet. 



The mechanism by which this is effected is shown in 

 dissection No. VII. Case 2. 



In this dissection the right wall of both test and 

 mantle have been cut away and the right wall of the 

 branchial sack split open longitudinally and flapped 

 back, so as to show the whole interior of the branchial 

 sack. 



We can now see, (1) running along the ventral wall 

 of the sack (right hand side of the observer) a groove 

 called the endostyle, and (2) running along the dorsal 

 wall of the sack (left hand side of the observer) a pro- 

 jecting fold called the dorsal lamina. 



Where the dorsal lamina ends, the opening of the 

 gullet (marked by a silver wire) is seen. 



The particles of food, washed into the branchial sack, 

 are caught by the secretion of the endostyle and are 

 carried forwards along the endostyle to the dorsal 

 lamina. They then pass backwards, matted together, 

 along the dorsal lamina to the opening of the gullet. 



The enlarged and coloured clay models in Case 3, 

 which have been made from the dissections, show 

 plainly the organs of respiration and digestion of the 

 typical Ascidian and their relations to the mantle and 

 test. 



The dissections enable us to realize that the breath- 

 ing organ of the Ascidians is on the same plan as that 

 of Amphioxus; but the other vertebrate affinities of the 

 Ascidians can only be illustrated here by drawings. 

 These, which are exhibited in Case 3, show that the 

 larva of the kind of Ascidian that we are considering 

 has a considerable resemblance to a frog's tadpole. It 

 has a head and a tail, In the tail there is a notochord, 



