ZOOLOGY. 

 FIFTH CIRCLE. AISTHESEOZOA. 



Class 13. Aistheseozoa. 



3426. An animal with all its organs of sense perfectly 

 developed, is a Thricozoon. 



3427. The nervous system emerges at length freely 

 above the other systems, and it is no longer its mass, but 

 its organs which impart character to the animal. The 

 nervous organs are, however, simply the organs of sense. 

 Through these therefore must the present differ from 

 the preceding class of animals. 



3428. Now too the senses first make their appearance 

 in a self-substantial manner above the other organs, 

 serving merely their own functions, and only by chance 

 those of others. 



3429. As in Birds the whole body was subordinated 

 to the thorax, in Reptiles to the abdomen, in Fishes to 

 the sex, in Insects to the tracheae, and so on ; in like 

 manner is it here subordinated to the system of the 

 senses or the head. 



3430. As the higher senses determine or define the 

 anterior part of the head, and are in their state of per- 

 fection provided with muscles ; so here the face or visage 

 is invested by flesh, whereby, properly speaking, a true, 

 namely, a moveable countenance, first originates. The 

 Aistheseozoa have a fleshy face. 



3431. All possess moveable eyes ; fleshy noses, which 

 stand open both externally and internally ; ears opening 

 outwards, and mostly provided with a moveable flap ; a 

 fleshy tongue, free in front, and moveable lips ; with at 

 least thoracic limbs and a skin covered with hairs. 



3432. In the Bird, Reptile, and Fish the face is 

 merely invested by tegument, nearly devoid of any 

 muscles, and therefore iimnoveable. They have a tegu- 

 mental face, which is incapable of producing any 

 expressions. 



3433. In the tegumental face the eyes are motionless. 

 and very rarely both directed so forwards that they can 



