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, Sdrtopoda, contains but one family, Pedal ion i>.'n , 

 and has only two genera. Pedalion and Ifp.'-arthra. and the latter of 

 these has but one known species, the former only two. Pedal i<m 

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

 organs are on the usual rotiferous plan, but its body bears no fewer 

 than six hollow limbs, ending in plumes like those of the Arthrojx.nl a. 

 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 running parallel to the 

 body's longer axis. In Hexarthra, 011 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 Rot! f era. 



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 Kile in 1853 ; their arthropodous limits 

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

 probable that the nearest relations of the Rotifera are the ART mm - 

 PODA; 1 at any rate, there is more probability in this suggestion than 

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



O t/ 



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; Dujardiii, 

 Sistoire naturelle des Zoujilii/tes infusoires, Paris, 1841; Pritchard, History of 

 Infusoria, 4th ed. London, i.861 (a comprehensive repertory of information) ; 

 Stein, Der Organismus der Infusionstliierc, Leipzig : Erste Abtheilung, 185'J ; Zweite 

 Abtheilmig, 1867 ; Dritte Abtheiluiig, Halite I. 1878. Saville Kent's Manual of tlie 

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

 Bromi's Thierreichs. For the Rhizopoda and Infusoria specially see Clapurede 

 and Lachmauu, Etudes sur les lufn.^iircs ct les Rliizopodes, Geneva, 1858-(il : 

 Cohn, in S/i'hiilil mid A"n///7,T/ '.v Zeitschrift, 1851-4 and 1857; Lieberkiilin, in 

 Mailer's Arcliiv, 1850, and Ann. of Nat. Hint. '2nd ser. vol. xviii. 185(1; Engelmami, 

 /.nr -\ntit rtj/ xr/ti<-///r der Infusionsthiere, 1862; and Professor Biitschli's Studien 

 iili/T die Coiijtif/itfioi/ ilcr Infusorien &c.., 1876. For the Rotifera specially see 

 Leydig, in Siebold itiul Kdlliker's Zrit.iclirift, Bd. vi. 1854; Gosse on Melicerta 

 ringens, in Quiirt.-lniirii.nl Microsc. Si-i. vol. i. 1853, p. 1 ; on the Manducatory- 

 Organs of Rotifera,!'////. Trim*. 1856; Huxley on Laciiiularia socialis in Trans. 

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

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

 /mil Kiil/iL; I-'K Zeitschrift, ls.s3; Bourne, l;t<t, ra, in the 9th edition of tlieEnci/- 

 c/ii/n,'i/in Briliinnica ', Joliet, ' Monographie des ifclici'i-tt's.' Arcliiv. zool. exper.ser. 

 ii. torn. i. p. 131 ; and Plate, Jencme/N Zeitsckr. 'six. p. 1. Tin Hufit'cra, or Wheel- 

 iiiiiin<ilriilrx, by Hudson and Gosse, Longmans, l.s.xn. This has been usefully sup- 

 jilcinentcd l>y Mr. C. F. Rousselet in two papers entitled 'List of New Rotifers since 

 ls,s'.,- in Journ. I!. .l/7r/Y/.vr. Soc. IS 1 .):;, ]>p. 45(l-,s, and 'Second List,' &c. in the 

 saint; journal for 1897, pp. 10-15. The bibliographical lists appended by Mr. Ilousse- 

 Ic-t will be found of much service, as since the publication of the work of Messrs. 

 Hudson and (lussc there lias been a ^reat re\i\al animiL;- the students of this Lrroup. 

 Mr. Slack's Murnl.s <</' Ponrl Lifr, '2nd edit. (London, 1*71), contains many interest 



I > ervationa on the habits of Infusoria and Rotifera. 



2 See his remarks on the relation of ihe Hot il'era to the Trochophore, in I!< j*. Brit. 



