Aulodrilus 599 



bifid, with thinner upper tooth, and capilliform. In A. pluriseta (Fig. 

 49, s. d.) bifid setae up to 10 in bimdle and up to 82 fi. long; 

 capilliform, up to 7 in bundle, the longest of them about 2Yj times 

 longer than the bifid. In A. pigueti (Fig. 18, s. d.) bifid setae, from 

 segment VI or VII backwards represented by spathulate setae, up 

 to 4 in bundle, up to 60 fi. long; capilliform setae, up to 4 in bundle, 

 about IY2 times longer than the bifid. 



Skin very glandular, especially in the anterior part of the body. 



In the muscle-system, besides the common layers, there are 

 well developed dorso-ventral muscle fibres in segments VI — 

 VIII in mature spécimens, especially in segment VII in A. pluri- 

 seta (Fig. 51, m. d. v.), in segment VII and in the posterior part 

 of segment VI, behind the spermathecal pores in A. limnobius. In 

 A. pigueti in segment VI they bave, on cross sections (Fig. 28, m. 

 spth.), a peculiar appearance of a semilunar compact mass of broad 

 fibres (author's spermathecal muscles) with extraordinarily large 

 nuclei. Some of thèse fibres, attached to the borders of the external 

 pores of the vestibula of the spermalhecae (Fig. 29, m. spth.), may 

 possibly serve to open them. 



Alimentary canal. The Salivary glands occupy four 

 anterior segments. Chloragogen cells commence from dissepi- 

 mentum VI/VII backwards. First intestinal enlargement 

 begins in A. pigueti (Fig. 38, A.) in the middle of segment VII, 

 in A. limnobius (Fig. 38, B) behind the dissepimentum VII VIII, 

 and in A. pluriseta usually (Fig. 38. C.) in the middle of segment 

 VIII, sometimes (young spécimens) more forwards. 



Vascular system. Contractile dorsal vessel, between the 

 dissepimentum VI/VII and the growing zone, lies on the left side 

 of the body, under the intestine and is attached to it (Fig. 11, 

 31 — 33, 50, V. d.). Ventral vessel in front of the dissepimentum 

 cited above, divided in A. limnobius (Fig. 10. v. v.) into two bran- 

 ches. At the posterior end of segment VI large contractile paired 

 heart (Fig. 29, 49, c). In ail other segments backwards, at the 

 same place, thin commissural vessels, by the displaced dorsal 

 vessel also displaced, su that the whole left commisure and a half 

 of the right enie lie on the left side and only the other half of 

 the right commisure on the right side of the hodj (Fig. 37 v. c). 

 In six anterior segments more or less (A. limnobius) developed 

 vascular plexus. 



