6 TOE ROTIFERA. 



The lioacl is sliaped somewhat like a truncated cone, with the larger end forward ; 

 posteriorly it is studded witli several small rounded lobes ; while from its anterior surface 

 rise throe fleshy protuberances, crownied with stout vibrating hairs called styles. 



Each side of the front of the head, or corona,'^ is rounded into a nearly circular lobe, 

 and along the rim of each lobe runs an unbroken row of smaller vibrating hairs, called 

 cilia, which are continued so as to meet each other on the dorsal sui-face. It is by 

 means of this apparatus that Brachiomis both swims and procures its food. 



As the head is seldom withdrawn into the lorica for more than a moment or two, 

 and as the cilia begin to jilay the instant it is protruded, Brachionus would have been 

 condemned to almost perpetual motion if it had not been for the foot. This organ is 

 provided at its extremity with two pincer-like processes, or toes (fig. 1, t) ; which, however, 

 do not pinch, but which can adliere even to glass by means of a viscid secretion that flows 

 through their tips. 



The foot-ylands (fig. 1, /</), which secrete this substance, are two club-shaped 

 organs running down the whole length of the foot. They are to be met with in nearly 

 all the Rotifera. 



The cilia, which are set closely round the edge of the corona, lash the water 

 with such fury that it is impossible usually to follow the action of any individual cilium; 

 but, by selecting an animal whose corona is close to the covering glass of the live 

 box, some spot can often be found where the action of the cilia is cheeked by their striking 

 against the glass; and, under these circumstances, it is easy to understand their action. 

 Each cilium lashes sharply downwards (like a wliip) on the corona, and then rises gradually 

 into its place again, to repeat the action continuously, so long as the corona is expanded. 

 As, however, the cilia do not do this simultaneously, but in turn, one after the other, in 

 very rapid succession, those that can be seen together at any given moment are in every 

 phase, from complete extension to complete depression ; thus givuig rise to various wave- 

 like illusory appearances, according to tlic illumination, and also to the plane on which 

 the objective is brought to focus. One of the most common of these appearances is that 

 of a toothed wheel, which is so well imitated by the Pkilodinada, that early observers 

 thought such wheels existed, and drew them like the escapement-wheel of a watch. ^ 



If a little carmine be mixed with the water, two beautiful coloured spirals will be 

 produced by the action of the ciliary wreaths, one on each side of the head leading dowai 

 to the buccal funnel. The orifice of the buccal funnel, or, as it will be termed, tlie buccal 

 orifice, lies in a niche on the ventral surface ; it is fringed by the ciliary wreath, which 

 here dips downi on either side of the corona, and passes romid the V-shaped openmg of 

 the buccal funnel (fig. 2, 5/)— that is, of the passage leading from the niche to the mastax. 

 The atoms brought by the ciliary currents pass down, the buccal funnel, which itself is 

 lined with cilia ; and, if uninterrupted, enter the mastax (figs. 1, 2, mx), a muscular bulb 

 containing the trophi (fig. 1 , ti) or tooth. But it is not every atom whirled down the buccal 

 funnel that is sufl'ered to reach the mastax ; for there arc two lip-like processes (fig. 2, Ip) 

 rising from tlie mastax, which can be seen every now and then thrust up and down the 

 buccal funnel ; and which by closing prevent the passage of morsels that are not to 

 the Eotiferon's taste. The sudden check, produced by the hps on the inflowing current, 

 always swoops out of the buccal funnel whatever the animal desires to reject ; and a 

 constant stream of rejected particles may be seen issuhig from the buccal funnel midway 

 between the spirals caused by the corona. 



The Mastax. 



The mastax (figs. 1, 2, vix; fig. C) is the muscular covering of the jaws or tropJti. 

 It has thick walls, and is slightly tiirce-lobed, each lobe investing one of the three prin- 

 cipal parts of which the trophi consist. There is an openmg in fi-ont towards the ven- 

 tral surface at the bottom of the buccal fuimel, whose walls here merge into those of 



' A name sugRestcd by Mr. Cubitt in lieu o{ trochal disk. 

 ' Baker on tlie Microscope, vol. i. Plate VIII. fig. 0, 1785. 



