1892.] FROM ALGERIA AND TUNISIA. 31 



The intestine has no typhlosole. The intersegmental septa are first 

 visible after segment v. Those separating segments vii./viii,, viii./ix., 

 ix./x., x./xi., xi./xii., xii./xiii. are thicker than the following ones. 

 Their insertion ventrally does not correspond with the interseg- 

 mental furrows, and this absence of correspondence is found also 

 further back. It is by no means unknown in other Earthworms, 

 and is, as a rule, limited to the anterior segments. Microscolex alge- 

 riensis has nephridia in all segments of the body commencing with 

 the second. They are paired and open in front of and a little to 

 the outside of the third seta. In dissection the nephridia are seen 

 to lie between the second and third setse on each side. There is a 

 long muscular end-sac, which in section was invariably much crumpled 

 owing to the thinness of its walls. 



The series of nephridia in this species is more complete than in 

 either of the other two species of the genus. It is important to 

 notice that after the xviith segment the nephridia have a thickish 

 coating of peritoneal cells. A difference of this kind often exsist 

 between the anterior and posterior nephridia in Earthworms, though 

 nothing of the kind has been mentioned by Rosa in this particular 

 genus. 



With regard to the vascular system the most noteworthy point 

 is the presence of three pairs of " hearts " in segments x., xi., and 

 xii. There are perioesophageal vessels in some of the segments 

 anterior to the xth, but these are not so well developed as those of 

 the three segments mentioned. The hearts of segment xii. are by 

 far the stoutest ; their diameter is at least twice that of the preceding 

 vessels, which are themselves of rather greater calibre than those of 

 segment x. There is no sub-nervian vessel. 



The firat'w is situated in the second segment, near to its posterior 

 boundary; the forward position of the brain is of interest. 



The generative system conforms to the general type met with 

 among the Cryptodrilidse. The testes are two pairs in segments x. 

 and xi. Opposite to them are the not remarkably large funnels 

 of the vasa deferentia ; the testes of segment xi. are partly attached 

 to the vas deferens just where it perforates the segment. The 

 sperm-sacs are in segments xi. and xii. ; they involve neither the 

 testes nor the funnels. The two vasa deferentia of each side of the 

 body remain perfectly distinct from each other up to their point of 

 opening on to the exterior. The two tubes run side by side in a 

 rather sinuous course, just below the peritoneum. In the xviith 

 segment are a pair of" prostates," or, as I prefer to call them, atria. 

 They are of the tubular form, and, as usual, are separated into a 

 glandular and a muscular portion. The minute structure of this 

 tube is precisely as in Acanthodrilus, Pontodrilus, &c. The atria 

 are not long, and are entirely contained within the xviith segment, 

 instead of being, as is frequently the case, prolonged into adjoining 

 segments. The exact mode in which the vasa deferentia open, I 

 have not been able to ascertain. In any case the two tubes, still 

 retaining their individuality, bore their way into the body-wall a 

 little in front of the point where the atrium opens ; they then pass 



