The Anatomy of Megascolides Australis. 167 



Circulatory System. 



A dorsal and ventral vessel are present. Lateral vessels, or 

 " hearts," connect the two in the 13th to 6th segments 

 inclusive, and from the 14th segment forward a lateral 

 vessel is present on each side, and a small supra-intestinal 

 branch in each segment. Posteriorly there is no direct 

 connection between the dorsal and ventral vessels, and the 

 former gives off two pairs of branches in each segment to 

 the walls of the alimentary canal, in which they come to lie 

 just externally to the cylindrical epithelium. 



Around the dorsal vessel posteriorly is a curious ensheathing 

 structure which gives off more or less solid diverticula into 

 the body cavity. These processes are filled with distinctly 

 nucleated, somewhat granular, polygonal cells. The nature 

 and function of this structure is as yet unknown. In each 

 segment it opens into the coelom close to the anterior septum. 



Nephridia (of Two Kinds). 



(1) Yery numerous, and varying in number in different 

 segments. They are especially numerous in the 13th to 

 20th segments, and are scattered irregularly over the body 

 wall. Each consists ot a much coiled duct which is clearly 

 intra-cellular, and surrounded by connective tissue very 

 rich in blood vessels. These nephridia have no internal 

 openings. (2) A series of larger nephridia in the middle 

 and posterior regions, one pair in each segment, with distinct 

 ciliated funnels opening internally. All the nephridia are 

 connected with a network of ducts lying beneath the coeloonio 

 epithelium, from which others pass off to open externally, so 

 that there are many irregularly arranged nep)hridio-iDores 

 in each segment. There seems to he one main duct 

 continuous from segment to segment on each side ventrally. 



Reproductive Organs. 



(1) Female. — Ovaries paired and attached by short stalks 

 to the septum bounding anteriorly the 13tli segment. The 

 two ciliated rosettes are in the same segment, and the 

 oviducts leading from them open externally on the I4tli 

 segment. 



The Kecep taenia seminis are laige, prominent, paired, 

 sac-like structures in the 8th and 9th segments. A curious 



