336 THE HISTORY AND SCOPE OF ZOOLOGY IX 



more complex structure resembling Molluscs, and he 

 gave them the name " Polyzoa." He discovered the 

 Pentacrinus europceus, and showed that it was the 

 larval form of the Feather- Star Antedon (Comatula). 

 He upset Cuvier's retention of the Cirripedes among 

 Mollusca, and his subsequent treatment of them as 

 an isolated class, by showing that they begin life as 

 free-swimming Crustacea identical with the young 

 forms of other Crustacea. Vaughan Thompson is a 

 type of the marine zoologists, such as Dalyell, Michael 

 Sars, P. J. Van Beneden, Claparede, and A]lman, 

 who during the present century have approached the 

 study of the lower marine organisms in the same 

 spirit as that in which Trembley and Schaffer in the 

 last century, and Swammerdam in the seventeenth, 

 gave themselves up to the study of the minute fresh- 

 water forms of animal life. 



It is impossible to enumerate or to give due con- 

 sideration to all the names in the army of anatomical 

 and embryological students of the middle third of 

 this century whose labours bore fruit in the modifica- 

 tion of zoological theories and in the building up of a 

 true classification of animals. Their results are best 

 summed up in the three schemes of classification 

 which follow below those of Kudolph Leuckart (b. 

 1823), Henri Milne-Edwards (1800-1884), and T. H. 

 Huxley (b. 1825), all of whom individually contri- 

 buted very greatly by their special discoveries and 

 researches to the increase of exact knowledge. 



Contemporaneous with these were various schemes 

 of classification which were based, not on a considera- 



