5G4 BIOLOGY. 



view an object together; the nostrils are frequently 

 devoid of a fleshy rim; the tongue often feather-like, 

 cartilaginous, or covered with teeth ; true fleshy lips are 

 wanting, as are frequently the teeth, with even the limbs 

 and digits, or these are divided into a number of rays, 

 forming either feathers, or fins ; in the Aistheseozoa there 

 are never more than five toes present, and if there be 

 fewer, then the number admits of being referred to some 

 crippling of the normal quantity, five. 



3434. It is remarkable, and serves to the discovery of 

 many laws, that the highest sense here appears for the first 

 time in its state of perfection. The eye in the Aistheseozoa 

 is present in a perfect condition throughout the class, 

 with the exception of the eyelids; the other organs of 

 sense are, on the contrary, exhibited in all their grada- 

 tions of structure. 



3435. It appears, as if the whole animal was first 

 perfected, when the eye is present with all its investment 

 or clothing. The eye of the Aistheseozoa has not simply 

 all its internal chambers and all its humours, but also 

 all its muscles ; it is moveable and has perfect eyelids, 

 with very few exceptions Ophthalmozoa. 



3436. The ear now begins to suffer arrest. Its com- 

 pletion is indeed the formation of an external concha or 

 flap for receiving the rays of sound, the hand being 

 repeated in the ear, and its skeleton constituted by the 

 auditory ossicles. This auditory hand occurs only in the 

 Aistheseozoa, and might serve as characteristic if it were 

 not wanting in many, while the eyelids are present. As 

 in the Whales, where the auditory passage can be, how- 

 ever, closed, an act which is not possible in any Bird. 

 The Bird must hear whether it will or no. 



In all Thricozoa the interior of the ear is perfect, 

 having cochlea, semicircular canals, tympanum, and, as 

 brachial parts, the three conjoined auditory ossicles. 

 The concha of the ear passes besides through all stages 

 of development, from having a simple margin to one with 

 most varied convolutions, lobes and opercula. 



3437. Still more than the ear does the nose undergo 



