BRITISH TUNIC AT A, 



INTRODUCTION.* 



NOTWITHSTANDING the great amount of labour which 

 has been bestowed on the investigation of the Tunica t a 

 for many years past, these curious and interesting 

 creatures do not yet appear to have found their final 

 resting-place in the classification of the Animal King- 

 dom. Naturalists are still divided in opinion as to 

 whether the Tunicata, together with the Bryozoa,t 

 should fall into rank at the bottom of the great 

 Molluscan sub-kingdom, whether they form an ab- 

 normal group which should be placed in the sub-division 

 Molluscoidea of Milne- Ed wards, or whether it is desir- 

 able to unite the Brachiopoda with them. 



Our recent researches, however, have forced upon us 

 the conclusion that the subjects of this monograph 

 are indeed true Mollusca closely related to the Lamelli- 

 branchiata much more closely than they are to either 

 the Bryozoa or the Brachiopoda ; and that, whilst the 

 two latter groups may be kept apart in a sub-class or 

 subdivision by themselves, the Tunicata should be 

 placed with the Mollusca. 



* Additions to the aiithors' MS. are placed within brackets in the usual 

 manner, except obviously editorial footnotes. A few verbal corrections have 

 been, made which are not so indicated. In the historical portion of the Intro- 

 duction the original spelling- of generic and specific names has been retained. 



t This term is here retained in deference to the adoption of it by the 

 authors, although the right of priority rests with Polyzoa. On this point, 

 and also on the intimate relationship existing between the Tunicata and the 

 Polyzoa, see Allnian's ( Fresh-water Polyzoa ' (Ray Society, 1856), and the 

 papers referred to on pages 6 and 43 of that work. 



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