INTRODUCTION. 19 



Hancock, published in 1870, " On the Larval State of 

 Nitlijulii ; with Descriptions of several new Species of 

 Simple Ascidians " (' Ann. Nat. Hist.,' ser. 4, vi), in 

 which he comes to the conclusion, from his own re- 

 searches and those of Van Beneden and Lacaze- 

 Duthiers, that there are two distinct modes of develop- 

 ment in closely-allied genera of the Tunicata, the 

 tadpole-condition being non-essential, a discovery which 

 he said might have some effect on the theory of the 

 relationship of this group with the Vertebrata. He 

 describes two new genera, Corella and Einji/rn, and the 

 following nineteen new species: Ast-i/lin ^l<ntn, A. 

 , A. nibro-tincta, A. ruJtirinnJn, A. rolnsta, A. 

 lx, A. cfitxxn, A. iitoi-nntit, A. /n-iuJnrta, A. elonr/atti, 

 A. <inin it, A. Xoi'uif/i/i, Cin-i'Uit larvdeformis, C. ofntn, 

 Oiona fascicularis, Molgula svmj_il<',i^ M. inconspicua, M. 

 complanata, and Eu</i/r <jl<>l><>xa. 



These species, with those previously described by 

 the authors, are for the first time figured in the present 

 Monograph.] 



Having now gone over the history of the discovery 

 of the Tunicata, both structural and zoological, we 

 shall give in detail a full account of the organization of 

 the entire class.* 



* As Albany Hancock died before the conclusion of his investigation 

 of the Tunicata, and had not written that portion of the introduction to 

 this work which would have embraced his latest views of their anatomy and 

 physiology, a paper which he contributed to the Linnean Society of London 

 in 1867 is here reprinted from the Journal of the Society by permission of 

 the Council. The only alterations which have been made in this paper are 

 the substitution for Ascidia of the generic names Ciona and Corella, and for 

 Molgula of the new generic name Eugyra, for certain species subsequently 

 referred to these genera by the author, and of Styela for Stycla, as Savigny's 

 genus erroneously appears in the paper ; also the insertion of the names of a 

 few species which wei-e then iindescribed, of sxib-headiugs, and of illustrations 

 from the author's drawings. Some portions of the paper which treat specially 

 of the anatomy and physiology of Ascidia and of a few other genera are 

 repeated, with or without modification, in the descriptions of those genera. 



