CLASSIFICATION OF ROTIFERA. 481 



whilst Prof. Leydig, who has recently devoted much attention to 

 the study of the class, regards them as most allied to the Crustacea, 

 and terms them ' Cilio-crustaceans,' Mr. Huxley, with (as it seems 

 to the Author) a clearer insight into their real nature, has argued 

 that they are more connected with the Annelida, through the 

 resemblance which they bear to the early larval forms of that 

 class (§489). Considered in this light, the Tardigrada might 

 seem to represent a more advanced phase of the same develop- 

 mental history.* 



* The following are the Treatises and Memoirs which (in addition to 

 those already referred-to) contain the most valuable information in 

 regard to the principal forms of Animalcules : — Ehrenberg, " Die Infu- 

 sionsthierchen," Berlin, 1838 ; Dujardin, " Histoire Naturelle des 

 Zoophytes Infusoires," Paris, 1841; and Pritchard, "History of Infu- 

 soria," 4th Ed., London, 1861 (a comprehensive repertory of informa- 

 tion). Fpr the Rhizopoda and Infusoria specially, see Claparede and 

 Lachmann, " Etudes sur les Infusoires et les Rhizopodes," Geneva, 

 1858-1861 ; Cohn, in " Siebold and Kolliker's Zeitschrift," 1851-4 and 

 1857 ; Leiberktihn, in " Muller's Archiv.," 1856, and "Ann. of Nat. Hist.," 

 2nd Ser., Vol. xviii. 1856 ; and the elaborate systematic Treatise of 

 Stein, " Der Organismus der Infusionsthiere," Leipzig, Erste Abtheilung, 

 1859, Zweite Abtheilung, 1867. And for the Rotifera specially, see 

 Leydig, in "Siebold and Kolliker's Zeitschrift," Bd. vi., 1854 ; Gosse on 

 Melicerta ringens, in "Transact, of Microsc. Soc," Ser. 1, Vol. iii. (1852), 

 p. 58 ; and "Quart. Journ. of Microsc. Science," Vol. i., p. 71 ; Williamson 

 on Melicerta ringens, " Quart. Journ. of Microsc. Science," Vol. i. (1853), 

 p. 1; Huxley on Lacinularia socialis, in "Transact, of Microsc. Soc," 

 Ser. 2, Vol. i. (1853), p. 1 ; and Cohn, in "Siebold and Kolliker's Zeit- 

 schrift," Bde. vii. ix., 1856, 1858. Mr. Slack's "Marvels of Pond Life" 

 (London, 1861) contains many interesting observations on the habits of 

 Infusoria and Rotifera. 



I I 



