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Rh very brief, are in general highly satisfactory. These circumstances have rendered this work the most valuable system that has ever appeared of the invertebrate animals; and it has formed the guide to most authors who have since written on the subject.

The phrase invertebrate animals originated with Lamarck, and it expresses, as Cuvier remarks, perhaps the only circumstances in their organization which is common to them all. They were previously known as white-blooded animals, a designation which was soon shown to be improper, by the discovery that an entire class (the annelides) possesses red blood. The system of Linnæus and Bruguière 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 discoveries 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 admitted the annelides to the rank of a separate class,