MEMOIR OF LAMARCK. 51 



very brief, are in general highly satisfactory. These 

 circumstances have rendered this work the most 

 valuable system that has ever appeared of the in- 

 vertebrate animals ; and it has formed the guide to 

 most authors who have since written on the sub- 

 ject*. 



The phrase invertebrate animals originated with 

 Lamarck, and it expresses, as Cuvier remarks, per- 

 haps the only circumstances in their organization 

 which is common to them all. They were pre- 

 viously known as white-blooded animals, a designa- 

 tion which was soon shown to be improper, by the 

 discovery that an entire class (the annelides) pos- 

 sesses red blood. The system of Linnaeus and Bru- 

 guiere formed the basis of his course when he first 

 began to lecture on the subject; he subsequently 

 adopted a new classification, founded on their 

 anatomy, which had been published in 1795. This 

 he afterwards modified in various ways, as new dis- 

 coveries were made, and as new relations suggested 

 themselves to him. In his system of invertebrata, 

 forming an octavo volume, published in 1810, he 

 adopted the class of Crustacea, and created that of 

 arachnides, a step which he judged necessary, in 

 consequence of some new information that had been 

 communicated to him on the heart and pulmonary 

 sacs of spiders. In a previous work he had ad- 

 mitted the annelides to the rank of a separate class, 



* The most recent and probably the best edition of the 

 Animaux sans Verttbres, is in eight volumes octavo, augmented 

 with notes by M. M. Deshages and Milne Edwards. 



