Has the insect a brain? It is a disputed question. The nervous apparatus which, in the molluscs, has not found, so far, a centre, tends, it is true, in the insect, towards centralization. Two longitudinal strings of nerves, which run through the entire length of the body, abut on the nerves of the head, which are not massed as in the higher animal. In the wasp, however, has been discovered a firm, whitish substance, strongly resembling the brain. But this would seem exceptional. Even in the head of insects remarkable for their intelligence, you will find only simple nervous ganglions, not differing in any respect from those which compose the two threads. This inferiority of organization does but render more surprising the superiority of the insect in art and sociability to all other animals, even to the principal mammals (with a single exception). Here at the highest point of the ladder, there at the lowest, it occupies, on the whole, a middle place; and is, as it were, in the scale of existence, an energetic mediator between life and death. [Illustration] NOTE 7.--Book ii., Chap. i. _Swammerdam._--We refer to the inaugurator and martyr of our science, the creator of the instrument which has enabled men to follow up his discoveries,--a great inventor in many senses,--specially for the preparation of anatomical specimens. The reader should study his _Biblia Naturæ_, in Boerhaave's edition, ornamented with fine illustrations (two vols. folio), and not in the incomplete French abridgment, published in the _Mémoires_ of the Academy of Dijon, which gives the scientific results, but no trace of the man. We do not undertake to write the history of Entomology. A good abridgment will be found at the end of M. Th. Lacordaire's _Introduction à l'Entomologie_. [Illustration] NOTE 8.--Book ii., Chap. iv. _The Insect as Man's Auxiliary._--The ingenious work which I here confute, and which, assuredly, cannot be read with gratification, is entitled,--_Les Insectes, ou Réflexions d'un amateur de la chasse aux petits oiseaux_, par E. Gand, _Lecture faite à l'Académie d'Amiens_ (26th December 1856). A remark which I make a few pages further on, in reference to the necessity of a popular teaching of natural history, well deserves to gain attention. The wealth and morality of the world would be doubled if this teaching could be universal. M. Emile Blanchard's important work, _Zoologie Agricole_ (in folio, 1854), gives the very useful history of the principal insects injurious to our ordinary or ornamental plants. M. Pouchet, in his excellent _Mémoire_ on the Cockchafer, enumerates the principal authors who have described the destructive insects. The United States Congress has entrusted to Mr. Harris the preparation of a history of them. [Illustration] NOTE 9.--Book ii., Chap. v.