INTRODUCTION. O 



presentation to the Institut de France. These memoirs 

 were read at the Institute respectively on the 6th of 

 February and the 1st of May, 1815, and were published 

 in the following year in Savigny's well-known work 

 entitled 'Memoires sur les Animaux sans Vertebres.' 

 Together with Cuvier's labours of about the same date, 

 they mark a great epoch in the study of the Tunicata. 

 Savigny's researches separated at once and for ever 

 the compound Ascidians and the Polypes, and enabled 

 Cuvier, from his previously-acquired information, to 

 suggest the. intimate relationship existing between the 

 compound and the simple forms, which hence became 

 an accomplished fact. 



Lesueur and Desmarest's researches on the compound 

 Ascidians were communicated to the Institute of 

 France in the same year [1815, in ' Bull. Soc. Philom.']. 



The ' Histoire naturelle des Animaux sans Vertebres ' 

 of Lamarck was published in the years 1815 to 1822. 

 This philosophical naturalist, having availed himself 

 of the then recent labours of the above distinguished 

 observers, instituted the class Tunicata to embrace the 

 simple and compound Ascidians, the latter including 

 Salpa. From a mistaken apprehension of the structure 

 of these animals he separated this class from the 

 Mollusca and placed it between the Radiata and the 

 Vermes ; yet in a certain sense he appears to have 

 appreciated the connection which exists between the 

 Ascidians and the Lamellibranchs, for he says that 

 " the series of the inarticulate animals, commencing 

 with the infusoires, is continued by the p1iji>cs, the 

 t tmiciers, the acalephes, and is terminated by the 

 molliistjiK's, of which the last orders are the cepJialopodes 

 and the heteropodes" 



In 1819 Cliamisso [' De Anim. Verm.'] gave to the 

 world his startling observations on the reproduction of 

 Sol pa, in the " alternation of generations," as he at 

 the time termed the phenomenon.* The report of 



* [For an account of Chamisso's observations see Steenstrup's ' Alterna- 

 tion of Generations/ translated by George Busk (Ray Society, 1845).] 



