INTRODUCTION. 



There is no large work on the Tunicata as a class, nothing of the nature of a 

 revision of the group, to which one may refer for the results of the numerous memoirs and 

 widely scattered papers which have been written on particular forms and special points 

 in anatomy. It seems therefore almost necessary to give, as an introduction to the 

 description of so many new genera and species of Ascidians, an outline of the history of 

 the group, a full bibliography, and a short account of the anatomy and histology of the 

 principal forms. 



HISTORY. 1 



The history of the literature of this, as of almost every other group of animals, extends 

 back to about 330 B.C., when Aristotle in his History of Animals gave, under the name 

 of Teihyum, a short account of a Simple Ascidian. He described briefly the external 

 appearance and the nature of the test, referred to the apertures and their inhalent and 

 exhalent functions, mentioned the mantle as a sinewy membrane lining the shell-like 

 substance, and evidently recognised the branchial and atrial chambers and the alimentary 

 canal — all the more important points in the macroscopic anatomy of the animal. 



The only other writers of classical times who mention Ascidians are Pliny and -Mian, 

 and they seem to have made little or no advance upon the knowledge of Aristotle. 



After this the record of Ascidiology takes a great leap over nearly fourteen centuries 

 — the dark ao-es of literature and science — and brings us to the middle of the sixteenth 

 century, when Bellonius and Rondeletius wrote treatises upon marine animals, some of 

 which we can recognise either from the figures or descriptions as Ascidians. 



Durino- the next hundred years Aldrovandus, Avicenna, Gesner, Jonston, Redi, and 

 Sloane, wrote on Marine Zoology, and contributed more or less to the knowledge of the 

 Tunicata. 



Schlosser first brought the Compound Ascidians into notice by his paper in the 

 Philosophical Transactions for 175G, containing a description of Botryllus, with some 

 observations by John Ellis. A few years later, A. Russel described and figured an 

 undoubted Boltenia from the coast of North America. Baster, shortly afterwards, in his 

 Opuscula Subseciva, described a species of Tunicate to which he gave the name Asddivm, 

 and compared its organisation with that of the oyster. Pallas suggested the union 



1 As a rule only works of considerable importance are referred to in this outline of the history. The complete 

 titles and dates of these and other works on the Tunicata will he found under the authors' names in the Bibliography. 



