43 



Notes of the Dissection of a Compound 



ASGIDIAN FOUND IN St. YiNCENT'S GuLF. 



By H. T. Whittell, M.D. 

 [Eead April 3, 1883.] 



Plate I. 



I do not know whether the Ascidian I am about to describe 

 has been found or named b}' earlier observers. It is new to 

 me, and differs in many respects from other Ascidians found at 

 the same locality, and from the description of the compound 

 Ascidians given in the text books of zoology. I have found 

 two specimens on different days during the last two months,, 

 both floating in the ripple at low water within a little distance 

 of the Glenelg jetty. 



The larger one was flattened, oval, and about three inches 

 long by two broad ; its thickness was about the third of an 

 inch. In the water it was not unlike a piece of boiled tripe. 

 It was soft and villose over its w^hole surface except at one 

 portion of the side, where it was smooth and membranous, and 

 in the centre of this smooth surface there was a small round 

 opening which looked like a mouth. This specimen was decom- 

 posing when I found it, and I could make nothing out of its 

 structure except that on cutting through it, I found a number 

 of bodies which I supposed to be ova. 



The second specimen was very much smaller, but in a good 

 state of preservation. This also had the side openiug at about 

 the same part as in the larger one. I preserved this as nearly 

 as possible in its natural condition, and before dissecting it^ 

 Professor Tate kindly gave me his opinion that I should find 

 it to be a compound Ascidian. After hardening the specimen 

 in spirit, I commenced the dissection by passing a fine probe 

 through the opening at the side. The probe moved freely in any 

 direction for about a quarter of an inch, but beyond this dis- 

 tance there was resistance. One point of a small scissors was- 

 then introduced into the orifice, and the opening was enlarged 

 above and below. An attempt was made from this point to 

 peel off the outer membrane. We know it is easy as a rule in 

 dissecting the solitary Ascidians to separate the outer test 

 from the membranous mantle or second coat. In the specimen 

 now under examination the separation could not be effected 

 except with the assistance of frequent snippings with the 



