256 FRANK E. BEDDAUD. 



§ Body-cavity. 



As is usual in earthworms, the first few segments are not 

 separated from each internally by regular septa; irregular 

 fasciculi of muscles attach the buccal cavity and the pharynx 

 to the parietes. The 5th segment is separated from the 6th 

 by the first regular intersegmental septum ; this and the 7th 

 which follow are specially thickened, and consist of several 

 layers of muscular fibres. These septa (fig. 48) fit into each 

 other like a series of cups ; they arise from points which corre- 

 spond accurately with the intersegmental furrows. 



The ccelom in this worm is further broken up into the com- 

 partments which lodge the testes and extremities of the vasa 

 deferentia, and into those which lodge the ovaries and the 

 spermatheca ; finally a special sac encloses the supra-intestinal 

 blood-vessel. All these coelomic chambers are specially 

 described under the different organs M'hich they enclose. 



As in other Oligochaeta (cf. Kiikenthal 13), the coelomic cor- 

 puscles are of two kinds. 



§ Vascular System. 



The supra-intestinal vessel exists in Heliodrilus, and 

 is connected with the hearts, as Perrier was the first to point 

 out in some other genera. 



In Heliodrilus this vessel is small, and lies in a special 

 coelomic space above the gut. A transverse section through 

 the supra-intestinal vessel and this perihsemal sac is illustrated 

 in fig. 46. The sac has exceedingly thin walls, wliich are con- 

 nected with the walls of the blood-vessels by irregularly dis- 

 posed trabeculse ; the interspaces are largely filled with cor- 

 puscles which have the characters shown in the figure ; these 

 cells are quite similar to those which occur in the walls of the 

 intestine. The inclusion of the supra-intestinal vessel in a sac 

 recalls the similar perihsemal space which I have described in 

 Deinodrilus (4) as surrounding the dorsal blood-vessel. 



The large "hearts" of Segments 11 — 13 communicate 

 with the supra-intestinal as well as with the dorsal vessel. The 



