13-2 THE ROTIFERA. 



ending in fans of imbrieateil seta\ in the conical sliape of the body, and in the broad 

 truncate corona ; but they differ strikingly in the way in which the limbs are set on the 

 body : for in PcdaUoti they are arranged around it parallel to its longitudinal axis, while 

 in Hexarthra, as in the Nauplius larva, they radiate from the centre of the ventral surface. 

 Nor is this the only difference. Hcxarihi'a's limbs are in three gi'aduated pairs, while 

 Pedalion's ventral limb is far longer than any of the others : moreover, Hcxarthia lacks 

 two long stylate appendages, ciliated at the ends, which are to be found on the posterior 

 end of Pedalion's dorsal sm-face. 



Genus PED.VLION, Hu^so7i. 



GEN. CH. Limbs arrancicd round the body in pairs, and paraUcl to its longitudinal 

 axis ; two stylate, ciliated appendages on the posterior dorsal surface. 



P. MUtUM, Hudson. 



(PL XXX. fig. 1.) 



Pedalion mirum . . . Hudson, ilfon. Jlficr. J. vol. vi. 1871, p. 121, pi. xciv. ; and p. 215. 



„ „ . . . „ Quart. J. Micr. Sci. vol. xii. 1872, p. 33H, pi. xix. 



„ „ . . . ,, JlioH. Mkt. J. vol. viii. 1872, p. 209, pi. xxsiii. 



„ ,, . . . Laukester, Quart. J. Mwr. Sci. vol. xii. 1872, p. 338. 



SP. CH. Ventral limb much the largest; dorsal limb on the 7nedian line ; lateral 

 limbs in two vnequal dissimil-ar p)airs ; the bases of all the limbs, lying in a transverse 

 section dehind the dorsal antenna; their free ends terminating in fans of imbricated' 

 seta. 



It was in July 1871 that I had the good fortrme to discover this remarkable Eotiferon 

 in a small road-side pond near the head of Nightingale Valley at Clifton. On placing a 

 specimen of it under the microscope I for a moment fancied that I had brought home by 

 mistake some Eutomostracous larva, for its outhue, its six limbs ending in fans of 

 imbricated setae, and its habit of jerking itself through the water, made it resemble the 

 ordinary NaupUus of a Cyclops. However, a brief examination showed it to be a true 

 Eotiferon, with a splendid corona and with mterual organs much Uke those of Triarthra 

 longiseta. The external form is extraordinary ; not only has it six well-developed limbs, 

 but all these Umbs are hollow, commimicating with the body cavity, and containing pairs of 

 opposing muscles prolonged into their interior. The arrangement of the hmbs too is more 

 effective for locomotion than that iu a Nauplius ; for in PedaUon they are attached in pau-s 

 to its anterior end, and lie parallel to the longitudinal axis of the body, so that their united 

 stroke acts at a great mechanical advantage ; but in the Nauplius lars'a the limbs radiate 

 from a spot on the ventral surface ; and, in consequence of this iaferior method of attach- 

 ment, produce a very feeble skip compared with the furious rush of PedaUon. The 

 corona is unusually large, and consists of two oval saucer-like lobes, so set as to give 

 together a heart-shaped appearance to the head. The ciliary wreath is double, and 

 precisely on the pattern of the Philodi/iada (PI. C, fig. 8|. Between the upper and 

 lower wreath is the usual groove along which the food is conducted to the mouth. On 

 either side the lower wreath dips down to the buccal orifice, which is prolonged ventrally 

 into a great curved lip, frmged with very large ciUa. The rather small mastax has two 



identical, and that the differences between my description and Dr. Schmarda's " reside principally in 

 the incompleteness of the details given by the latter, and are consequently differences of omission 

 rather than anything else." It is difficult to understand how it can be an " omission " to describe and 

 draw all the sjj- legs as radiating from a spot on the ventral surface, while (on the supposition of the 

 identity of the two creatures) there is only one on that surface, and all lie round the body and parallel 

 to its length. Keilher can it well be an " omission " or an " incomplete detail " to say that there are 

 ttco legs of equal size longer than all the others, when there is only one such leg. Indeed, were Dr. 

 Sclmarda really capable of ths gross blunders attributed to him by Mr. Deby, the whole of his observa- 

 tions would be worthless. 



