792 MICROSCOPIC FORMS OF ANIMAL LIFE 



a forked jointed foot, the fork being formed of two toes varying 

 greatly in size and shape, but all secreting the viscous fluid already 

 mentioned. The great majority of the Rotifera belong to the 

 Plo'ima. 



The fourth order, Scirtopoda, contains but one family, Pedalionidce, 

 and has only two genera, Pedalion and Hexarthra, and the latter of 

 these has but one known species, the former only two. Pedalion 

 (figs. 4, 5, 8, Plate XVII) is an extraordinary creature. Its internal 

 organs are on the usual rotiferous plan, but its body bears 110 fewer 

 than six hollow limbs, ending in plumes like those of the Arthropodti, 

 and worked by pairs of opposing muscles which traverse their entire 

 length. These limbs are arranged round the body, some- on the 

 dorsal, some on the ventral surface, and all tunning parallel to the 

 body's longer axis. In Hexarthra, on the contrary, all the limbs 

 are on the ventral surface, and are arranged radiatingly. There is 

 no foot in either Rotifer; but in Pedalion there are two ciliated 

 club-like processes at the posterior extremity, rising above the 

 dorsal surface and secreting a similar viscous fluid to that secreted 

 in the toes of other Rotifera. 



This strange creature was discovered by Dr. C. T. Hudson in a pond 

 near Clifton in 1871 ; Hexarthra was discovered by Dr. Schmarda 

 in a brackish ditch near the Nile in 1853 ; their arthropodous limbs 

 give them a strong resemblance to a Nauplius larva, and make it 

 probable that the nearest relations of the Rotifera are the ARTHRO- 

 PODA ; L at any rate, there is more probability in this suggestion than 

 in that of Professor Hartog that they are allied to the Pilidium- 

 larva of Nemertine worms. 2 



1 The following treatises and memoirs (in addition to those already referred to) 

 contain valuable information in regard to the life-history of animalcules and their 

 principal forms: Ehrenberg, Die Infusionsthierchen, Berlin, 1838 ; Dujardin, 

 Histoire naturelle des Zoophytes infusoires, Paris, 1841; Pritchard, History of 

 Infusoria, 4th ed. London, 1861 (a comprehensive repertory of information) ; 

 Stein, Der Organismus der Infusionsthiere, Leipzig : Erste Abtheilung, 1859 ; Zweite 

 Abtheilung, 1867 ; Dritte Abtheilung, Hiilfte I. 1878. Saville Kent's Manual of the 

 Infusoria, 1880-1 ; and Professor Biitschli's Protozoa (1880-1) in the new edition of 

 Bronn's Thierreichs. For the Rhizopoda and Infusoria specially see Claparede 

 and Lachmann, Etudes sur les Infusoires et les *Rhizopodes, Geneva, 1858-61 ; 

 Cohn, in Siebold ^lnd Kolliker's Zeitschrift, 1851-4 and 1857; Lieberkiihn, in 

 Mutter's Archiv, 1856, and Ann. of Nat. Hist. 2nd ser. vol. xviii. 1856; Engelmann, 

 Zur Naturgeschichte der Infusionsthiere, 1862 ; and Professor Biitschli's Studien 

 iiber die Conjugation der Infusorien &c., 1876. For the Eotifera specially see 

 Leydig, in Siebold und Kolliker's Zeitschrift, Bd. vi. 1854 ; Gosse on Melicerta 

 ringens, in Quart. Journ. of Microsc. Sci. vol. i. 1858, p. 1 ; on the Manducatory 

 Organs of Eotifera, Phil. Trans. 1856; Huxley on Lacinularia socialis in Trans. 

 Microsc. Soc. ser. ii. vol. i. 1853, p. 1 ; Cohn, in Siebold und Kolliker's Zeitschrift, 

 Bde. vii. ix. 1856, 1858 ; Dr. Moxon, Trans. Linn. Soc. 1864 ; Karl Eckstein, Siebold 

 und Kolliker's Zeitschrift, 1883; Bourne, Rotifera, in the 9th edition of thei///r//- 

 clopcedia Britannica ; Joliet, ' Monographic des Melicertes,' Archiv. zool. exper. ser. 

 ii. torn. i. p. 131 ; and Plate, Jenaische Zeitschr. xix. p. 1. The Rotifera, or Wheel- 

 animalcules, by Hudson and Gosse, Longmans, 1889. This has been usefully sup- 

 plemented by Mr. C. F. Eousselet in two papers entitled ' List of New Eotifers since 

 1889,' in Journ. R. Microsc. Soc. 1893, pp. 450-8, and ' Second List,' &c. in the 

 same journal for 1897, pp. 10-15. The bibliographical lists appended by Mr. Rousse- 

 let will be found of much service, as since the publication of the work of Messrs. 

 Hudson and Gosse there has been a great revival among the students of this group. 

 Mr. Slack's Marvels of Pond Life, 2nd edit. (London, 1871), contains many interest- 

 ing observations on the habits of Infusoria and Rotifera. 



2 See his remarks on the relation of the Rotifera to the Trochophore, in Rep. Brit* 



