6 BEITISH TUNICATA. 



this curious mode of reproduction was received with 

 astonishment, as it was deemed to be unparalleled in the 

 history of animals, although it was well known to the 

 discoverer of Sotri/Uus that it was a compound animal 

 which increased by pullulation. Pallas announced 

 this fact on the authority of Gartner in his ' Spicelegia 

 Zoologica ' in 1774. Chamisso's observations were 

 confirmed by Krohn [in 1841].* 



In 1821 H. Kuhl and van Hasselt discovered the 

 flux and reflux of the blood in Salpci ; that curious and 

 characteristic feature in the circulation of the Tunicata, 

 that ebb and flow in the current, first setting 1 for some 

 time in one direction and then flowing in the opposite. 

 Since this peculiar action of the blood-current was 

 made known there has been no lack of subsequent 

 observers who have verified this extraordinary fact in 

 almost every genus in the entire class ; and, indeed, 

 there is no difficulty in witnessing the marvellous 

 sight, as no preparation is required ; all that has to 

 be done is to place under the microscope a young 

 individual of almost any species so as to secure the 

 necessary transparency, and the phenomenon may be 

 observed for any length of time. 



The next important discovery was made by Audouin 

 and Milne-Edwards in 1828 ['Ann. Sci. JN T at.,' xv] 

 Avhile they sojourned at the lies Chausey. There these 

 two celebrated observers ascertained for the first time 

 that the compound Ascidians undergo a metamorphosis; 

 that these animals, so immovably fixed in their adult 

 state, are free during the first period of their existence 

 and swim freely about by the aid of a long, broad tail. 

 It is evident, however, that Savigny had previously 

 seen the first, or tadpole, state of Botri/llus, as in 

 Plate xxi of his ' Memoires ' he gives two figures of 

 it, but calls them, in the description of the plate, " two 

 side-views of an e^ef arrived at its mature state.' 



~ 



* [Also in the same year by Sars, who said of the Salpse that " it is not 

 their larvae which are developed into the perfect animal, but the progeny of 

 the larvae." See Steenstrup, op. cit., p. 46. j 



