The animals of the first primary division he defines as destitute of feeling, and moving only by their excited irritability; and he assigns as their character, the absence of a brain and of an elongate medullary mass; senses wanting; forms various; articulations rarely existing. The animals of the second division feel, but they obtain from their sensations only _perceptions_ of objects, a kind of simple ideas which they are unable to combine with each other in order to form complex ones. They possess no vertebral column, but have a brain and most frequently an elongate medullary mass; some distinct senses; organs of motion attached under the skin; the form symmetrical, the parts arranged in pairs. The _intelligent_ animals, forming the third grand division, feel, and acquire ideas capable of being preserved, and execute operations between these ideas which furnish them with others; and they are intelligent in different degrees. They possess a vertebral column, a brain and spinal marrow; distinct senses; organs of motion fixed to an interior skeleton, and symmetrical forms, the parts being placed in pairs[19]. This general distribution of animals has not been very much approved of by naturalists; and Cuvier asserts that it is neither founded on their organization, nor an exact observation of their faculties. The degree of intelligence observed in the different classes, would certainly lead most observers to give a very different position to several, from that which they have obtained in the above scale. The _insecta_ and _arachnides_, for example, which are made to occupy the lowest place among the sentient races, are undoubtedly entitled to the rank assigned to the _mollusca_ and _cirrhipedes_; for there can be no comparison in this respect between a hive-bee or an ant, and an imperfectly organized and almost inanimate mollusc. At a subsequent period, in consequence of some new discoveries made by M. M. Savigny, Leseur, and Desmarets, he separated certain tribes from the polypi, and formed them into a distinct class under the name of _ascidiens_. Some new views likewise occurred to him regarding the general arrangement of animals, and instead of presenting them in a simple series, he divided them into two subramose series, as follows:-- [Illustration: