112 M. Blanchard on the Circulation in Insects. (Hyalonema) ; and in some instances, from a mixture of membra-nous tissue with the earthy matter, they resemble cork. 4. Among the calcareous corals the texture or density of the coral is often of little importance, as it may vary in different parts of the same specimen, according to their full exposure to the free ocean waters or not. In species with stellate cells there is always a definite number of rays to the adult cell, excepting among those that bud in the discs, and this number is some multiple of four or six, and usually of both. The characters of the cells — whether immersed or occu-pying a prominent calicle; and, internally, deep and open at bottom, or transversely septate, or spongy cellular or solid, — are important ; also the peculiarities of the lamellae, whether entire or not, equal or irregular, exsert or included. In transverse sections of the stellate cells, the number of rays (when adult), the diameter, and the character of the centre and of the interstices, are generally good characteristics for species. The corals of Alcyonaria never have rays to their cells or tubes ; the Madreporacea have never more than twelve rays ; the Caryo-phyllacea and Astrseacea have always more than twelve ; and the last order is distinguished by having the interval between the cells lamello-striate (see p. 109, III. 2) internally, with few ex-ceptions, as well as externally. This brief review of the characteristics of zoophytes has pre-pared the way for an exposition of the classification into which the species naturally fall. [To be continued.] XIII. — On the Circulation in Insects. By Emile Blanchard*. The celebrated author of the ( Anatomie Comparee/ finding no other vessels in insects than the dorsal one, believed that no true circulation existed in these articulated animals. According to Cuvier, the trachese ramifying throughout the entire body of the animal, the air in them must proceed in search of the blood, just as, in animals having a pulmonary or bronchial respiration, the blood is conveyed to the air. Since his time, many anatomists have studied the circulation in insects. They have usually selected transparent larvse which have allowed them to distinguish, through the tegumentary en-velope by the aid of the microscope, currents of liquid blood. In this manner Carus observed a circulatory movement in the larvae of the Ephemeridse and Agrions. Wagner, Bowerbank, Newport, and others have verified these facts. According to these observers, -. * Translated from the Comptes Rendus for May 17, 1817.
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