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. 



