CLASSIFICATION Iv 



may be represented something after the manner of the 

 different points of a compass. This idea, which some modern 

 writers think subhme, is clearly a mistake, and is certain to 

 be dispelled when we have a deeper and wider knowledge of 

 organisation." Yet it is now known to represent the 

 facts much more nearly than the linear arrangement of 

 Lamarck. 



The first great service of Lamarck to classification was 

 in establishing the distinction between vertebrates and 

 invertebrates. Aristotle, indeed, had detected the profound 

 difference between these two groups : but he had taken as 

 his standard of differentiation the presence or absence of 

 blood : a highly defective standard which was not to any 

 great extent improved by Linnaeus. It was reserved for 

 Lamarck, in his course of lectures at the Muséum in 1794, to 

 direct attention to the immense taxonomic importance of 

 the vertebral column, and to set up that great primary 

 division of the animal kingdom, which was long regarded 

 as final. 



The remainder of Lamarck's achievements in classification 

 lie within the realm of Invertebrata : for it was with these 

 animals that his professional work at the Muséum was 

 exclusively concerned. At the time when he assumed the 

 task of organising the vast collection of animals accumulated 

 there, Linnseus's classification of invertebrates into insects 

 and worms was still current. In that same course of lectures 

 in 1794, he broke up the class of worms to form four new 

 classes : molluscs, worms, echinoderms, and polyps. These 

 divisions had already been suggested by Bruguière as orders 

 in the old class of worms. Lamarck did not then touch 

 Linnaeus's class of insects, which comprised the whole phylum 

 of arthropods. 



The arrival of Cuvier in Paris in 1795 produced a general 

 stimulation of biology, from which Lamarck was not slow 

 to profit. The medusae and other radiating coelenterates 

 had been grouped by Linnaeus with the molluscs, and that 

 classification was still maintained. Lamarck removed them 



