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Show 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 intersegmental 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 algeriensis 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 setae 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 pericesophageal 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 brain 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 Cryptodrilidae. 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 |