Linnean Transactions. 269 



collected in Fox Channel during the late Northern Expedition." 

 Re-urging the now almost undisputed position that zoology cannot 

 be satisfactorily studied without comparative anatomy being taken 

 for its basis, he proceeds to apply the aids to be thence derived to 

 the illustration of this osculant group, between the polype Jcrita 

 and the Acephalous Mollusca. It would be difficult without the 

 aid of the beautiful plates appended to his descriptions to convey 

 an adequate idea of the species which he has dissected, the Bol- 

 tenia reniformis, Cystingia Griffithsii^ and Dendrodoa glandaria : 

 for this we must therefore refer to the volume itself, contenting 

 ourselves with extracting such portions of his arrangement as may 

 furnish io those who study these animals a general view of his 

 method of distributing them. He divides the Tunicata into an 

 aberrant group ? Tethya^ and a normal one ? Thalida. The first 

 of these, in which the mantle adheres to the envelope or test only 

 at its orifices, the branchial one being surrounded by a mem- 

 branaceous ring, which is in general supplied with tentacula as in 

 Polypes, comprises three families : 1. Ascididce^ Animals simple 

 and fixed, having their orifices externally irregular ; Generic 

 Type, Ascidia : 2. Botryllidce, Compound and fixed, having their 

 orifices externally regular ; Generic Type, Polyclinum : and 3. 

 Lucidce, Compound and floating, having their branchial cavity 

 open at the two extremities; Generic Type, Fyrosoma. The 

 second, or normal? group, in which the mantle adheres every- 

 where to the envelope, and the branchial orifice is provided 

 merely with a valvule, contains only one family at present known, 

 the Blphoridce, of which Salpa forms the generic type ; another 

 family thus remaining to be discovered, and to reward the industry 

 of the assiduous and qualified collector. 



Considerable confusion having arisen in the application of the 

 trivial names, pedunculata, clavata^ and globifera^ to the different 

 species of Ascidia comprised in the genus BolteniUy Sav., Mr. 

 MacLeay has given a synopsis of these. They are three in num- 

 ber, and are all peculiar to the Arctic Seas. From the synonyms 

 appended to the species it appears that the Bolfenia ovifera Sav. 

 is the Ascidia globijera of Lamarck, and the A. pedunculata of 

 Shaw and Bruguieres ; that the B.fusiformis Sav. is the A. pedunn 



