GENERAL CLASSIFICATION 161 



singular that we have to set them apart as constituting a special 

 class. 



Seeing that the cirrhipedes have a shell, a mantle and no head or 

 eyes they cannot be crustaceans ; their jointed arms prevent us from 

 placing them among the anneUds, and their ganglionic longitudinal 

 cord does not allow us to unite them with the molluscs. 



TABLE OF CIRRHIPEDES. 



Tubicinella. Balanus. 



Coronula. Anatifa. 



Remark. We see that the cirrhipedes still resemble the annelids 

 by their gangUonic longitudinal cord ; but in these animals nature is 

 preparing to form the molluscs, since they have like them a mantle 

 covering the inside of their shell. 



MOLLUSCS. 

 (Class X. of the Animal Kingdom.) 



Oviparous animals with soft unjointed bodies, and having a variable 

 mantle. 



Respiration by very diversified gills ; no spinal cord, nor ganglionic 

 longitudinal cord, but nerves terminating in an imperfect brain. 



The majority are enclosed in a shell ; others have one that is more or 

 less completely embedded ivithin them, and others again have none at all. 



Observations. 



The molluscs are the most highly organised of invertebrates ; that 

 is to say, their organisation is the most complex and the nearest to 

 that of the fishes. 



They constitute a numerous class which terminates the invertebrates, 

 and which is sharply distinguished from the other classes by the fact 

 that the animals composing it are the only ones which, although 

 having a nervous system Uke many others, have neither a gangUonic 

 longitudinal cord nor a spinal cord. 



Nature is here about to begin the formation of the system of organisa- 

 tion of the vertebrates ; and appears to be preparing for the change. 

 Hence the molluscs, which have altogether lost the type of articula- 

 tions, and the support given by a horny skin to animals belonging to 

 this type, are very slow in their movements and appear in this respect 

 even more imperfectly organised than the insects. 



Finally, since the molluscs constitute a hnk between the inverte- 

 brates and the vertebrates, their nervous system is intermediate, 



