ZOOLOGY. 507 



3121. Through the separation of the viscera from the 

 remaining substance, this must necessarily remain behind 

 as a hollow cyst or tegument investing the former. The 

 true free tegumental formation is therefore by no means 

 accidental, but is necessarily bestowed with the viscera 

 in the course of animal development. This tegument is 

 peritoneum. There are animals which are invariably 

 bicystic, but consisting of concentric cysts abdomens. 



Around the ventral integument, however, the vas- 

 cular system also forms its tunic ; this is the branchial 

 membrane or operculum pleura, mantle. There 

 are tri-cystic animals intestine, abdomen, and thorax 

 disposed concentrically around each other Mussels. 

 Their body is therefore not articulated, but its parts are 

 still inserted within each other. 



The Vascular animals are consequently multiplied 

 Protozoa ; or Mucus-animals of the second power 

 Ovum? 



The sense of feeling ascends upon its second stage, 

 when its organ, having been freed from the mass of the 

 body, surrounds the viscera as a self-substantial tegu- 

 ment. The feeling is then no longer one of a merely 

 general character, but is a definite perception of external 

 objects, a passive power of feeling. 



3122. True muscles could not as yet originate in this 

 skin, and that for obvious reasons, although fibres are pre- 

 sent; for the former are to be brought under the significa- 

 tion of arterial fibres. 



3123. Cilia, when furnished with fibres by whose 

 agency they are rendered moveable and susceptible of 

 inversion, are called tentacula, which here occur under 

 every variety of form. 



3124. Would we compare the Vascular animals with 

 the plants, they must then represent their ducts, liber, 

 and stalk. The heart is the stalk, the arteries liber, the 

 veins tubes or ducts. These animals have assumed also 

 upon the whole the cauline or cylindrical form Cauline 

 animals. 



3125. From their having obtained in addition to the 



