WHEEL-BEARERS 289- 



will be worth while to devote a few minutes' careful ob- 

 servation to this structure before us, especially as it is here 

 seen with more than usual brilliancy and clearness. 



The mastax, then, which you see in the centre of the 

 animal, just below the level of the beautiful flower-like 

 wheels, consists as usual of three sub-globose lobes; one 

 on each side appropriated to each malleus, and the third 

 descending toward the ventral aspect, which envelops the 

 incus. The mallei are more intimately united to the rami 

 of the incus than in the former type, each uncus forming, 

 with its ramus, a well-defined mass of muscle, enclosing 

 the solid parts, and in form approaching the quadrature 

 of a globe; two flat faces opposing and working on each 

 other. Across the upper surface of the mass the uncus 

 is stretched, as three long parallel fingers arched in their 

 common direction, and imbedded in the muscular sub- 

 stance; their points just reaching the opposing face of 

 the ramus, and meeting the points of the opposite uncus, 

 when closed. The manubrium is much disguised, by be- 

 ing greatly dilated transversely, forming three bow-like 

 loops of little solidity, to the chord of which the fingers 

 are soldered, not articulated. The surface of the dense 

 muscular mass displays striae parallel to the fingers, and, 

 as it were, continuing their number toward their dorsal 

 extremity, becoming fainter till they are imperceptible. 

 These striae do not disappear when the muscular parts are 

 dissolved by potash; and hence I infer the existence of a 

 delicate investiture of solid substance similar to that of the 

 teeth, etc., enclosing the muscular mass. 



The incus, which cannot be separated from the mallei, 

 thus consists of two portions, corresponding to the rami 



in Brachionus, etc., each of which forms the lower part 



SCIENCE 13 



