718 RECORD OF CgRRENT RESEARCHES RELATING TO 



served in tlio Gammaridfe, and may possibly have the same function 

 as the Malj^ighian vessels of the Tracheata, have not yet been 

 observed by Clans in any of the Hyperida ; it is possible, although 

 we have no certain proof of it, that their function is performed by 

 the epithelium of the small intestine. 



Circulatory System. — The heart extends from just behind the 

 cephalic region to as far as the middle of the sixth thoracic segment, 

 and is provided with three pairs of ostia ; the muscular bands of the 

 heart are formed from two lateral rows of cells, between which there 

 is a dorsal and vonti-al median suture ; there are two arteries which 

 arise from an elongated fissure, and have at their base two obliquely- 

 set ostia ; they are placed in the third and fourth segments of the 

 thoracic region, and there is, in addition, in some genera a third pair 

 of arteries in the fifth thoracic segment ; the vessels pass into the 

 perienteric canal system of the body-cavity, and their walls are 

 formed by a transparent membrane of connective tissue, in which ai'O 

 contained, just as in the aorta of the Copepoda, oval nuclei. The just 

 mentioned perienteric canal system is thus formed : there is attached 

 to the ventral wall of the heart a septum, formed of large cells, which 

 extends transversely across the body-cavity ; a second septum holds a 

 similar relation to the enteron, and the body-cavity is thus divided 

 into three haemal canals, which are separated by connective tissue, 

 and communicate with one another by definite orifices. These 

 primary canals extend into the cephalic region, and are supplemented 

 by a number of peripheral secondary canals along which the blood 

 courses in a very regular manner ; as in all Arthropoda, the fluid 

 starts from the heart in two directions, going forwards by the cephalic 

 aorta and gastric artery, and backwards by the aorta abdominalis and 

 the hinder gastric vessels. 



Nervous Systcvi. — Exclusive of the sub-oesophageal ganglionic 

 mass, the ventral coi'd consists of five thoracic and four abdominal 

 ganglia ; the last of these is formed by the concrescence of three 

 ganglia, which are separate in the embryo, and supplies the fourth, 

 fifth, and sixth abdominal segments. The sub-cesophageal mass 

 corresponds to six ganglia, or, with the ganglionic centre for the 

 antennae, which is placed in the commissures, to seven. The peri- 

 pheral nerves do not take their origin from the " dotted substance," 

 but from the ganglionic cells of their own ganglion, from the pre- 

 ceding ganglion, and from the cerebroid mass. This last contains a 

 well-developed system of commissures, part of which extends into the 

 large optic ganglia. Turning to the eye itself, we find that this is 

 surrounded by an investing sheath of considerable strength, which is 

 formed by a continuation of the outer nervous covering of the brain ; 

 the cornea is formed by a special investment of the hypodermis, while 

 the eye continues to grow with the body, by the continuous formation 

 of new peripheral elements ; this organ is, as is well known, remark- 

 able in the Hyperida for its division into two completely sej^arated 

 optic areas ; in corresj)ondencc with this the optic fibres are found to 

 be arranged in two bundles, which arise from difiereut portions of the 

 ganglion. 



