Ix INTRODUCTION 



arthropod type, and if his scheme of classification had 

 admitted of groups superior to classes, there is no doubt 

 that he would have combined the insects, arachnids and 

 crustaceans into one phylum, altogether separate from the 

 molluscs, though the annelids and cirrhipedes are regarded 

 by him as intermediate forms. 



Lamarck divides molluscs into two orders of Cephalic and 

 Acephalic. The latter of course consist mainly of the 

 modern lamellibranchs. One section of this order, however, 

 contains the brachiopods, and another section the tunicates, 

 which he took to be molluscs. Lamarck's Order II. are the 

 Cephalic molluscs. It is divided into the three sections of 

 pteropods, gastropods and cephalopods. Nearly half the 

 animals included by Lamarck under the name of cephalopods, 

 consist of Foraminifera ; most of the remainder are genuine 

 cephalopods. One of the Foraminifera, which Lamarck 

 mistook for a cephalopod, is Orbulites, which here occurs 

 for the second time in his animal scale ; for this animal had 

 already been once named as belonging to the polyps. 



These are the main features of Lamarck's classification of 

 the invertebrates. That he should have evolved these ten 

 classes, with their various orders, out of Linnseus's insects 

 and worms is an achievement of no small magnitude. We 

 now come to the vertebrates, to whose classification Lamarck 

 never made any contribution. I may therefore rapidly 

 run through the classification which he here adopts from 

 what he believed to be the best authority of his time. 



Class XL contains the fishes. They are divided into two 

 orders of Cartilaginous and Bony fishes ; though Lamarck 

 includes among the Cartilaginous fishes a number of our 

 modern ganoids and teleosts. This order commences with 

 the hagfish and lamprey, correctly placed together as cyclo- 

 stomes : Linnaeus had previously regarded the hagfish as 

 a worm. The second order of Bony fishes mainly consist of 

 " Holobranchs," or fishes with complete gills. These holo- 

 branchs are divided into thirty sections, largely determined 

 by the character and position of the fins, as also by the gills. 



