OF THE EOTATOEIA. 415 



essentially the same structui-e as that of the teeth of Notommata described by 

 Mr. Dalrymple {PhiJ. Trans. 1849), and by Mr. Gosse (XXXVI. 6) {T. M. S. 

 1851), and veiy different from the stirrup -shaped " armature " represented 

 by Ehrenberg and Dujardin in Lacinularia. Prof. Huxley notes, moreover, 

 the omission of the two pieces constituting the " incus," in the description 

 given of the apparatus by Leydig. 



The last-named author has attempted no general description of the dental 

 organs, and has, in the specific details, so briefly adverted to their structure, 

 that he would seem to attach to them little importance. He has, however, 

 figured the maxillse of Notommata Sieboldii (XXXVII. 31), wishing especially 

 to represent the transversely-striated muscles acting upon them. He men- 

 tions the maxillae, which occupy the spacious angular maxillary bulb, as ex- 

 hibiting a bifid or forked portion, hooked at the ends, with a spine projecting 

 from the inner side, and a margin on the outer side : to the latter the strong 

 muscles for opening and shutting the maxillae are afiixed. The transverse 

 striation of the muscles is particularly brought into view by pressure on the 

 apparatus. Cohn (Zeitschr. 1855) has some very precise details respecting 

 the structure of the dental mechanism of Hydatina senta, and of two or three 

 other Kotatoria ; but it would lead us beyond our scope, to transfer them to 

 our pages. 



The most elaborate attempt to unfold the true structure of the maxillae, 

 and to reduce all the varied foi-ms to a common type the essentials of 

 which are always detectable notwithstanding any degree of general modifi- 

 cation, has been made by Mr. Gosse. The diversity of descriptions met with 

 among writers on the Rotatoria, respecting the maxillae, is materially due to 

 the hmited examination, undertaken by any one of them, of those organs, — 

 each observer having studied some one, or at most but a few species, and 

 then describing the peculiar maxillary organs met with as pervading the 

 whole class : such as is essential to the discovery of their true relations, a 

 comparison of their structure among all the genera, has been neglected. The 

 right mode of study seems to have been undertaken by Mr. Gosse ; but his 

 conclusions require to be tested by repeated observation {Phil. Trans. 1855). 

 His method of manipulation, for the purpose of examination, is well worth 

 noting. He says {op. cit. p. 424), — " In the course of experiments with 

 various chemical reagents on these animals, I found that a solution of potash 

 had the effect of instantly dissolving the flesh and most of the viscera, leaving 

 the general integument, the walls of the pharyngeal bulb, and all the solid 

 parts of the manducatory apparatus uninjui-ed. In most cases, also, the last- 

 named organs are expelled from the visceral cavity by the contraction of the 

 integuments, so that they float at large in brilliant clearness, undimmed by 

 intervening tissues, and as patent to observation as when crushed between 

 plates of glass, with the advantage of all the parts being unbroken and re- 

 taining their relative positions. Now, by turning the screw of the compres- 

 sorium, flattening or deepening the drop of water, waves were communicated 

 to it, by means of which the floating bulb, being nearly globular, was made 

 to revolve irregularly, and thus to present, in succession, various aspects to 

 the eye." 



To display his researches ever so briefly, we must first introduce his no- 

 menclature. The gizzard or enclosing maxillary bulb, he calls the mastacc 

 (XL. 20) ; and declares it to be a muscular trilobate sac. The maxillce con- 

 sist of two geniculate bodies {mallei) (XL. 20 h), and a third on which they 

 work {incus) (XL. 20 /). Each malleus is of two parts — 1, the manuhium 

 (c), and 2, the uiicus {e), — united by a hinge joint. The manubrium is a 

 piece of irregular form, consisting of carince of soHd matter, enclosing three 



