SouTHEEN — Monograph of the British and Irish Oligochceta. 143 



nephridia resemble those figured by Claparede. The arrangement of the 

 nephridia in this genus agrees with the description of Fhreatothrix lyragensis, 

 as given in the text by Vejdovsky (28. p. 55) ; but in the figure (28. PL xi., 

 fig. 18) the segments are numbered one further behind. These numbers are 

 copied by Beddard (1. p. 218), and Michaelsen (21. p. 59). The second pair 

 of nephridia are shown with a short glandular investment, somewhat 

 resembling that of the present species ; but the other nephridia are 

 without it. 



The reproductive organs agree very closely with those of S. lieringianus 

 (fig. 8, d). The spermathecte are in the 9th segment. They have an almost 

 spherical ampulla, and a slender duct of about the same length. There is no 

 crystal in the ampulla. The male ducts open at the back of the 10th segment. 

 The penes are pointed, and about as long as half the diameter of the body. 

 The atrium is oval and thickly coated with the prostate glands. The testes 

 lie in segments 9 and 10. The first pair are attached to the anterior septum ; 

 the second pair lie on the floor of the segment. The ovaries are attached to 

 the front of segment 11. The oviducts are short and wide, and open between 

 the 11th and 12th segments. There are two pairs^ of sperm-sacs, the first 

 pair being small and confined to segment 8. The second pair commence in 

 segment 9, and stretch into segment 13. Frequently the sperm-sacs on one 

 side are undeveloped. The egg-sac is dorsal and unpaired. It opens into the 

 11th segment, and may stretch as far back as the 21st segment, according to 

 the stage of maturity. The reproductive organs of >S'. gabretce Yejd., were 

 recently investigated by Martin (18. p. 21). On comparing fig. 8, D, with the 

 diagram he gives (page 22, fig. 3), it will be seen that there is general agree- 

 ment as to the position of the various organs. He states, however, that the 

 sperm-sacs lie in segments 8 and 10-13. Fig. 8, d shows that the posterior 

 sperm-sacs project into segment 9. It may be, however, that the sperm-sac 

 was forced into segment 9, owing to the contraction of the specimen when it 

 was being killed and fixed for sectioning. 



Vascular System. 



It is the vascular system of this species which chiefly characterizes it. 

 The most striking characteristic of the family Lumbriculidas, and one which 

 distinguishes it from all other Oligochasta, is the occurrence of blood-glands or 

 blind contractile appendages to the blood-vessels. These appendages are 

 usually covered with chloragogen-cells, and possibly some interaction takes 

 place between these cells and the blood. On the other hand there is evidence 

 to show that these contractile sacs have a respiratory function. 



B.I.A. PROC, VOL. XXVn., SECT. B. [Z] 



