'20 BRITISH TUNICATA. 



ON THE ANATOMY AND PHYSIOLOGY OF THE 



TUNICATA. 



By ALBANY HANCOCK, F.L.S. 



[From ' Journ. Linn. Sue.,' Zool., vol. ix, pp. 309-336.] 



HAVING employed myself recently in the investigation of the 

 Timicata (their anatomical structure and physiology) with a 

 view to a monograph of the British species, which my late 

 lamented friend Mr. Alder and I had undertaken to prepare 

 for the Ray Society, some very interesting anatomical facts 

 have come to light ; and I now propose to give a succinct 

 account of the more important of these, believing that they 

 cannot fail to be acceptable to those naturalists who may have 

 studied these low but not by any means unattractive mollusks. 

 I reserve, however, for some future occasion a more complete 

 and detailed description. 



When I took up this subject, I had little expectation of 

 meeting with much that was new ; for perhaps in no other 

 group of the Molluscan subkingdom has the anatomy been so 

 frequently and so ably investigated as it has been in the 

 Tunicaries ; and, indeed, in them, all the leading points appear 

 to have been fully determined ; but experience proves, never- 

 theless, that much of interest has been left unobserved, quite 

 sufficient to reward the labour of re-examination, and seem- 

 ingly ample enough to modify some of the more important 

 morphological determinations. 



This unexpected result may, in part, be owing to the fact 

 that, while my researches have been chiefly confined to the 

 simple Ascidians, it is apparently to the compound, social, and 

 pelagic forms that the greatest attention has been hitherto 

 given. Thus it happens that numerous details have remained 

 until now unnoticed in the former group. 



THE TUNICS. 



There is something fresh to record in nearly all the visceral 

 organs, but in none so much perhaps as in the vascular and 

 respiratory systems. Before entering, however, 011 such new 

 matter, it will be well to say a few words respecting 1 the tunics, 

 so characteristic of these animals. In all the various forms 

 that have been examined there is no great difficulty in deter- 



