68 THE ROTIPEEA. 



are all in constant motion. The action of the former, or principal, wreath (PI. V. figs. 2c, 

 4, pw) draws the particles floating in the water into two spiral currents, which are tangen- 

 tial to the groove on either side of the disk. The action of the latter, or secondary wreath 

 (PI. V. figs. 2c, 4, sw] drags the particles, as in their spiral path they strike the groove, out 

 of that path into the groove itself, and hurries them along its windings towards the buccal 

 funnel. At the two points where the groove on each side joins the buccal funnel are two 

 fleshy knobs (PL V. fig. 2c, tr), which can be seen in constant motion ; either regulating 

 the force of the current, examining the moving atoms, 6r possibly performing both offices 

 at the same time. The ciliated edges and sides of the buccal funnel conduct a portion of 

 the stream down to the mastax ; while another, and apparently the larger portion, rushes 

 over the ciliated chin. 1 If a little carmine be added to the water, it is a pretty sight to 

 see the coloured spirals form on both sides of the corona, while two processions of 

 crimson atoms wind in and out under the margin of the petals, one on the left hand, and 

 one on the right ; each starting from the dorsal gap, and dashing at last down the 

 buccal funnel, or over the chin. (PL V. figs. 2c, 4, ch,} But the whole of the ciliary 

 apparatus has not yet been noticed. Beneath the chin there is a hemispherical hollow 

 (PL V. figs. 2c, 4,cc) which is furred with minute cilia. It is in this cup that M. ring ens 

 and M. conifer a mould their pellets, as will be described further on 2 ; it is present also 

 in M. tubicolaria and M. Janus, but its function in these species is unknown. 



The Nutritive System. The buccal funnel (PL V. figs. 2c, 2rf, 4, bf) slopes downwards, 

 and somewhat dorsally, towards the mastax. It is ciliated throughout, and has a pair of 

 chitinous lips (fig. 2rZ, lp] similar to those described at p. G. These lips are in frequent 

 motion, now opening and shutting, now moving up and down the funnel, evidently 

 selecting and rejecting the food : if an objectionable morsel attempts to pass, " it is 

 astonishing to see how the little quick jerk, which the lips give, tosses it up into the 

 central stream of waste and drives it away." 3 Should this morsel be unusually large, 

 the mastax itself aids the lips in their upward jerk. On each side of the buccal funnel 

 and above the mastax is a clear organ (PL V. fig. 2d, scj) whose surface is spheroidal. 

 The two have been described as salivary glands by some observers, and as mere stays 

 to the mastax by others. They are obviously elastic, and move up and down with its 

 every motion. The mastax (fig. 2d, mx) consists of three confluent lobes, presenting a 

 trefoil outline in vertical section ; each side-lobe contains a malleus, and the bottom- 

 lobe grasps the incus. The malleo-ramate trophi (PL V. fig. If) are almost precisely 

 similar to those already described. 



The food flows between the lips, and after having been torn by the sharp teeth of the 

 mallei, and crushed by the ridged inner surfaces of the rami, passes through a short 

 ciliated ossophagus (fig. 4, &}, and so enters the stomach (fig. 4, s). This is a long 

 cylindrical sac, with very thick walls of large cells, lined with cilia. A partial con- 

 striction usually separates it from the intestine (i). The walls of this latter are thinner 

 and more transparent, and their cilia longer. The distinction between the stomach and 

 intestine is obliterated when the stomach is much distended with food, but is usually 

 present, and is often rendered obvious by the difference of colour in the contents of the 

 two. Those of the intestine revolve under the action of its cilia ; and when the pellet 

 thus formed is ready for extrusion, the animal lifts its cloaca above the rim of its cup 

 pushes up the pellet, bends downwards over it, and then dexterously shoots it across 

 its shoulder into the current flowing from the chin. By this means the fajces are 

 carried away out of the currents of the trochal disc. 



The Secreting System. The so-called salivary glands I have already noticed. There 



1 Judge Bedwell (Mon. Micr. J. vol. xviii. 1877, p. 216) describes in M. ringens a hemispherical 

 cushion, placed at an angle on that side of the buccal funnel which is opposite to the chin. He thinks 

 that it is a highly sensitive organ, which, by altering its facial configuration, directs the streams that 

 go down the buccal funnel and over the chin, and drives suitable particles in appropriate directions. 

 I have not, however, been able to confirm those observations. 



' Pp. 70, 71. * Judge Bedwell (loc. cit.). 



