150 ZOOLOGICAL PHILOSOPHY 



crustaceans. Their soft elongated body, which in most of them simply 

 consists of rings, makes these animals appear as imperfect as the 

 worms with which they used to be confused. Since, however, they 

 have arteries and veins and breathe by giUs, these animals are quite 

 distinct from the worms and should be placed with the cirrhipedes 

 between the crustaceans and the molluscs. 



They have no jointed legs,^ and most of them have on their sides 

 setae or bundles of setae which take the place of legs : they nearly all 

 have suckers and feed only on fluid substances. 



TABLE OF AKNELIDS. 



Obdeb 1. — Cbyptobeanch Annelids. 

 Planaria [Triclad. H. E.]. Furia (?). 



Leech. Nais. 



Lemea [Copepod. H. E.]. Lumbricus. 



Clavella [Copepod. H. E.]. Thalassema. 



Obdeb 2. — Gymnobbanch Anneuds. 



[Polychaets. H. E.] 



Arenicola. — 



Amphinoma. Terebella, 



Aphrodite. Amphitrite. 



Nereis. Sabellaria. 



— Siliquaria [mollusc. H. E.]. 



Serpula. Dentalium [mollusc. H. E.]. 

 Spirorbis. 



CIRRHIPEDES. 

 (Class IX. of the Animal Kingdom.) 



Oviparoiis and testaceous animals without a head or eyes, but having 

 a mantle which covers the inside of the shell, jointed arms whose skin 

 is horny, and two pairs of maxillae. 



Respiration by gills ; a ganglionic longitudinal cord ; vessels for cir- 

 culation. 



Obsekvations. 



Although only a small number of genera belonging to this class are 

 yet known, the character of the animals contained in these genera is so 



1 In order to perfect these animals' organs of locomotion, nature had to abandon 

 the system of jointed legs, which are independent of a skeleton, and to estabhsh the 

 system of four Hmbs depending on an internal skeleton, which is characteristic of 

 the most perfect animals ; this is what she has done in the annehds and moUuscs, 

 where she has paved the way for commencing with the fishes the type of organisation 

 peculiar to vertebrates. Thus in the annelids she has abandoned jointed legs, and 

 in the molluscs she has gone still farther, — she has discarded the use of a ganglionic 

 longitudinal cord. 



