510 BIOLOGY. 



they also are devoid of flesh asarcose animals like all the 

 preceding ones. 



3137. In the branchiae, however, it is only the cauline 

 portions which become horny, while their ramules con- 

 tinue to perform the respiratory function. The branchiae 

 therefore are appended to the extremity or roots of the 

 feet ; or rather these latter form thejDranchial arches. 



Annulate animals, having true or hornified and like- 

 wise annulated feet, are called Crustacea or Crabs. 



Thus, in these animals the sense of feeling obtains spe- 

 cial and moveable organs ; they are Tactile animals. 



Tactile organs are prolongations of tegument moved 

 by muscular fibres, which in some degree adapt them- 

 selves by pressure unto the forms of objects, or have the 

 power of seizing and retaining them such as feet, 

 antennae, maxillae, palpi. 



3138. But if the tegument be entirely converted into 

 horn, and the respiratory vessels have in this way disap- 

 peared within it, then the internal respiratory organs are 

 formed by inversion of that part of the tegument which 

 is between the rings, and through these openings the 

 air penetrates to the internal parts stigmata, tracheae. 



3139. The tracheae can first of all originate when the 

 respiratory process has attained its highest development, 

 or, in other words, when the creature breathes air. 



3140. Lastly, in the air-breathing Ancyliozoa even the 

 external branchial lamellae harden and are converted into 

 wings Pterozoa, Insects or Flies. 



The wings of Insects do not correspond to the wings 

 of birds; they are not feet, but pedal appendages or 

 branchice, and thus are no new or unknown organ. 



Circle IV. Sarcose Animals. 



3141. The second animal province may be regarded 

 as the fourth stage in the self- substantial development of 

 the anatomical systems, although, properly speaking, it 

 ranks as regards its value or worth upon a level with the 

 three former circles, and resolves itself directly into three 

 stages, which accord with its three systems. But since 



