292 EVENINGS AT THE MICKOSCOPE. 



you see it, you probably discern little resemblance iu 

 its parts to the same organ in Brachionus, and yet 

 essentially it is formed of the very same constituents ; 

 and as it is very instructive to observe the modifica- 

 tions, in different animals, of a common model of any 

 particular organ, it will be worth while to devote a 

 few minutes' careful observation 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 towards 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 oj)posing 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 

 being greatly dilated transversely, forming three bow- 

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

 fingers are soldered, 7iot articulated. The surface of 

 the dense muscular mass displays striae parallel to 

 the fingers, and, as it were, continuing their number 

 towards their dorsal extremity, becoming fainter till 

 they are imperceptible. These stria3 do not disappear 



