326 OLIGOCHAETA 



This species, originally described and figured in many of its details by Eisen (13), 

 has been more recently studied by Michaelsen (15), who has added to Eisen's 

 account. The species is to be distinguished by the form of the outgrowths of the 

 nerve-chord which are very large and lobed and do not cover the fibrous part of the 

 chord. There seem to be no perivisceral corpuscles. 



(a) Pachydrilus profugus, Eisen. 



Enehytraeus pagenstecheri, Eisen, Ofv. Svensk. Akad. 1872, No. i, p. 133. 

 Archienchytraeus profugus, EiSEN. Ofv. Svensk. Akad. 1878, No. 3, p. 73. 

 Pachydrilus profugus, Levinsen, Vid. Med. 1883, p. 231. 



Paehydrilus pagenstecheri, Vejdovsky, Syst. u. Morph. 1884, p. 41 (in part.). 

 Pachydrilus profugus, Michaelsen, Abh. Nat. Ver. Hamb. 1889, p. 34. 



Definition. Length, 1 8 mm. ; number of segments, about 50 ; setae, 8-9 per bundle. Brain 

 concave in front. Spermalhecae with a distinctly marked duct rather longer than pouch 

 and leset for its whole length with oval glands. Hah. — Greenland. 



This species, formerly confounded with P. -pagenstecheri by Eisen, was subsequently 

 recognized by him as distinct ; the two species differ in — among other points — the 

 characters of the setae, which in the present form are more or less uniform in size. 

 In the definition of the species I therefore follow Eisen's more recent description of 

 the species; in his earlier account he gives the length as 13 mm., the number of setae 

 as 3-9, which number suggests that, after all, some specimens at any rate of the true 

 P. pagenstecheri were included. 



(3) Pachydrilus verrucosus, Clapaeede. 



Pachydrilus verrucosus, Clapabede, M^m. Soc. Phys- Gen. 1863, p. 83. 



Definition. Length, i2,mm.; number of segments, about 40 ; setae, ^-^ per bundle ; integument 

 covered with minute papillae. Spermatheca without distinct duct. Hah. — Hebrides. 



This species has been investigated by CLAPARiiDE, who has described and figured 

 a good many points in its anatomy; he has not, however, described the brain, or 

 mentioned whether the spei-matheca is furnished with glands as it is in other species. 

 I include Taubee's Pachydrilus verrucosus among the synonyms, and do not relegate 

 it, as does Michaelsen, to his own species Pachydrilus fossarum ; as Taubee merely 

 gives the name and the locality where he met with the worm, it does not appear to 

 me that there is any justification for doubting his identification. 



