CXXXll INTRODUCTION. 



which those who continue to adopt Thompson's name rely, 

 and to justify their departure from what is^ it must be ad- 

 mitted, the prevalent usage. If the question were merely 

 one of priority, it might be readily and conclusively settled, 

 and in this case the recognized laws of scientific nomen- 

 clature would come in to restrain the license of individual 

 systematists, and enforce a wholesome uniformity. But 

 other elements besides mere date are involved ; and in these 

 the real difficulty lies. 



So far as the mere question of time is concerned, the 

 facts are conclusive in favour of Thompson's claim, as long 

 since shown by Busk (1852)^ and Allman (1856) f. The 

 term Biyozoa first made its appearance in the ' Symbolse 

 Physicse ' in 1831 J ; but Thompson's ' Researches,' in 

 which he proposed the name Polyzoa for the type of struc- 

 ture which he had demonstrated in the polypide of the 

 Ascidian zoophytes §, were published in 1830. We learn 

 from himself that his discovery was made as early as 1820; 

 so that he really anticipated Grant (1827) and Milne- 

 Edwards (1828), though the publication of his results was 

 delayed. That his name was published before Elirenberg's 

 it is impossible to doubt. Cams, however, urges that it 

 had been previously employed by Lesson (in the ' Voyage 

 de la Coquille ') for a genus of Tunicates, and that this 

 fact alone must prevent its adoption ||. But the genus 

 Polyzoa of Lesson appears not to have made good its place 

 in molluscan nomenclature ; I cannot learn that it is found 



* " On the priority of the term Polyzoa for the Ascidian polypes," Ann. 

 N. H. ser 2, x. p. 352. 



t 'A Monograph of the Freshwater Polyzoa,' pp. 5, 6. 



\ ' Symbolte Physiese ; seu icoues et descriptiones animalium ' &c., 1828- 

 1831. 



§ This I take to be what Thompson intended. 



II ' Ilandbuch der Zoologie,' erster Band, ii. Halfte, p. 790. 



