412 Miscellaneous, 



surrounding this organ, does not exist, and that its description is 

 partly due to the detachment of the cuticular substance underneath 

 the lung, the separation of which has led to the belief in the exist- 

 ence of a floor or partition between the ventral surface of the body 

 and the corresponding face of the organ in question. 



The blood comes into direct contact with the leaves, entering 

 between them by their dorsal edges, and then falls into the sub- 

 pulmonary chamber, whence it can only escape by tlie vessel which 

 conducts it to the pericardium, and thence to the heart. — Comptes 

 Bendus, tome cxiii. no. 2 (July 13, 1891), pp. 94, 95. 



On the Arterial System of Isopods. By M. A. Schiteidee. 



Among the characters which the study of the arterial system had 

 permitted us to assign to Isopods, was the existence of a vascular 

 collar, anterior to the nerve-ring, giving off the subneural vessel, 

 and furnishing in conjunction with the latter the arteries of the 

 buccal appendages. 



Nevertheless, in the Annelids, as well as in the Myriapods and 

 Arachnids, the great aortic arch is, as in the case of the Vertebrates, 

 situated behind the brain. Are we really confronted with an 

 anomaly ? My injections of PorcelUo and Ligia enable me to reply 

 in the negative. 



Independently of the two arteries which continue the aorta in 

 front, below the antennary arteries, running along the edge of the 

 nervous collar, there exist, behind this collar, two arteries which 

 arise from the aorta in the immediate neighbourhood of the point 

 from which the ophthalmic artery starts. A peculiarity which 

 distinguishes them is the loop formed by each around the base of 

 insertion of a little ligament upon the stomach. They pass round 

 the digestive tube, give off an anastomosing branch to the mandibular 

 artery, and unite below the stomach and above the inferior nervous 

 mass, thus describing a ring comparable in every respect to that of 

 the Arachnids, and which is, manifestly, the great aortic arch of the 

 Isopods, dorsal in position with reference to the neivous system. 

 From this arch there pass, to the right and left, the arteries of the 

 buccal appendages, with the exception of those of the mandibles, 

 which start from a trunk common also to the antennary arteries. 



Moreover, I convinced myself in the two types in question, that 

 one or several anastomoses between the ophthalmic artery which 

 arises behind the brain and the antennary arteries which are in 

 front of it, unite these two trunks into a median arch or into two 

 arches approaching the median plane, in such a way that this arch, 

 with the aorta which subtends it, describes a vertical vascular ring 

 which recalls that of the Amphipods. 



Thus there fall to the ground two characters, one of which 

 created a unique position for the Isopods from the point of view of 

 general morphology, wliile the other tended to separate them pro- 

 foundly from the Amphipods. — Conq^tiS licndus, tome cxiii. no. 7 

 (August 17, 1801), p. 31G. 



