56 



THE MICROSCOPE AND ITS REVELATIONS. 



FIG. 311. 



antenncB or palpi of higher Articulata, the single organ being replaced in 

 many Rotifera by a pair, of which each is furnished at its extremity with 

 a brush-like tuft of hairs that can be retracted into the tube. The 

 esophagus, which is narrow in the Rotifer, but is dilated into a crop in 

 Stephanoceros (Fig. 312) and in some other genera, leads to the masti- 

 cating apparatus (Fig. 310, e), which in these animals is placed far 

 behind the mouth, and in close proximity to the stomach. The Masti- 

 cating apparatus has been made the subject of attentive study by Mr. P. 

 H. Grosse; who has given an elaborate account of the various types of 

 form which it presents in the several subdivisions of the group. 1 The 

 following description of one of the more complicated will serve our 

 present purpose. The various movable parts are included in a muscular 

 bulb, termed the mastax (Fig. 311, a), which intervenes between the 

 buccal funnel (m) and the oesophagus (p). The mastax includes a pair 

 of organs, which, from the resemblance of their action to that of 

 hammers working on an anvil, may be called mallei, and a third, still 



more complex, termed the incus. 

 Each malleus consists of two prin- 

 cipal parts placed nearly at right 

 angles to each other, the manu- 

 Irium (c), and the uncus (e) ; these 

 are articulated to one another by 

 a sort of hinge-joint. The former, 

 as its name imports, serves the 

 purpose in some degree of a han- 

 dle; and it is the latter which is 

 the instrument for crushing and 

 dividing the food. This is done 

 by means of the finger-like pro- 

 cesses with which it is furnished 

 at the edge where it meets its fel- 

 low; these being five or six in 

 number, set parallel to each other 

 like the teeth of a comb. The in- 

 cus also consists of distinct arti- 

 culated portions, namely two 

 stout rami (a) resting on what 

 seems a slender footstalk (h) 

 termed the fulcrum ; when viewed laterally, however, the fulcrum is seen 

 to be a thin plate, having the rami so jointed to one edge of it that they 

 can open and close like a pair of shears. The uncus of each malleus falls 

 into the concavity of its respective ramus, and is connected with it by a 

 stout triangular muscle (i), which is seen passing from the hollow of the 

 ramus to the under surface of the uncus. It is difficult to say with cer- 

 tainty what is the substance of which these firm structures are composed; 

 it is not affected by solution of potass, but is instantly dissolved without 

 effervescence by the mineral acids and by acetic acid. Besides the mus- 

 cles already described, a thick band (/) embraces the upper and outer 

 angle of the articulation of the malleus; and is inserted in the adjacent 

 wall of the mastax; and a semi-crescentic band (k) is inserted by its broad 

 end into the inferior and basal part of the uncus, and by its slender end 

 into the middle of the inner side of the manubrium; the former of these 



Masticating Apparatus of Euchlanis deflexa: 

 a, Mastax; c, manubrium, and e, uncus, of 

 Malleus; g, rami, and h, fulcrum, of Incus; i, mus- 

 cle connecting ramus and uncus; j, mucles pass- 

 ing from malleus to mastax: fc, muscle connecting 

 uncus and manubrium; m, buccal funnel; n, saliv- 

 ary glands; p, oesophagus. 



" Philosophical Transactions," 1856, p. 419. 



