CLASSIFICATION ]ix 



VI., consists of the arachnids, estabHshed for the first time 

 by Lamarck himself. It comprises two orders, the first of 

 which corresponds to our modern class of arachnids, while 

 the second ("arachnids with antennae") includes our 

 modern myriapods, together with one or two insects such 

 as the louse and silver-fish. 



Class VII. are the crustaceans, divided into the two orders 

 of those whose eyes are at the end of stalks, and those whose 

 eyes are sessile. In the next class, that of the annehds, 

 Lamarck discerns the commencement of a tendency on the 

 part of nature to abandon the articulatory type in favour 

 of the vertebrate type. Thus he finds that annelids no 

 longer have jointed legs, as in the classes immediately pre- 

 ceding. The class is divided by Lamarck into two orders, 

 of which the first — ^the Cryptobranch annelids — is a mixture 

 of various ill-assorted animals, including a triclad and two 

 copepods.^ The order includes Lumhricus and Nais : though 

 curiously enough, in his later and more systematic work, 

 Lamarck restored Nais to his class of worms, removing it 

 from the annehds. The second order, the Gymnobranch 

 annehds, consists of polychaets, with the addition of two 

 molluscs at the end. 



Class IX. are the cirrhipedes, with only four known genera. 

 They are intermediate between the annehds and Class X. 

 containing the molluscs. Lamarck regarded the molluscs 

 as the highest class of invertebrates. For some time, he 

 says, Nature had been making preparations for originating 

 the vertebrate plan of organisation. In the moUuscs those 

 preparations are completed. The articulatory system ac- 

 cordingly vanishes : and the slow movements of molluscs 

 are due to the fact that the class is midway on the road of 

 development from an external to an internal skeleton, and 

 therefore possesses the advantages of neither. It is to be 

 noted that Lamarck had a very clear conception of the 



have three setse in their sucking-organ. As a matter of fact they always have four ; 

 though two are often united together, so as to give the appearance of only three. 



1 The triclad (Planaria) is removed to its proper position in the Animaux sans 

 Vertebres. 



