DESCRIPTIONS OF GENERA AND SPECIES 325 



CLAPAEiiDE's P. krohnii is incidentally described in his memoir upon the anatomy of Lumbn'cus 

 (1, p. 571, footnote) ; this worm was found in the soil near Kreuznach. It is 5-9 mm. long, and consists 

 of about fifty segments. But CLAPABtoE gives no other characters that are of any use in differentiating 

 the species ; it is hardly necessary to point out that the above are insufficient for this purpose. 



CzERNiATSKY has described the following species of 'Pachydrilus' : — P. gracilis, P. proximus, 

 P. affinis, P. similis, P. lacustris, P. charkoviensis, and P. opacus. These are allowed by Vaillant, who, 

 however, does not regard the descriptions as sufficient — a conclusion which most will share with him. 

 All these species, together with P. cavicola (Joseph), are placed by Michaelsen at the end of his 

 Revision of the Enchytraeidae as ' species inquirendae.' 



The well-characterized forms can be divided into two sets according to whether 



the spermatheca has or has not a duct distinct from the pouch. 



The following table will serve to discriminate the species : — 



A. Spermatheca without a duct distinct from the pouch. 



(i) Copulatory glands present. 



{a) nearly covering nerve-chord P. lineatus. 



(6) not covering nerve-chord P. litoreus. 



(2) No such structures. 



{a) Setae, 3-5 per bundle P. verrucosus. 



(6) Setae, 5-8 per bundle P. subterraneus. 



B. Spermathecae with a distinct duct marked off from pouch. 



(i) Copulatory glands present. 



i. Setae more numerous ia ventral bundles . . P. pagenstecheri. 

 ii. Setae equal in both bundles. 



(a) Copulatory glands lobed P. nervosus. 



(6) Copulatory glands, not lobed P. maximus. 



(2) No copulatory glands. 



i. Setae not more than 9 in a bundle . . .P. profagus. 

 ii. Setae as many as 14 in a bundle P. minutus. 



(i) Pachydrilus nervosus, Eisen. 



Arohienohytraeus nervosus, Eisen, Ofv. Svensk. Akad. 1878, No. 3, p. 73. 

 Bnchytraeus nervosus, Vejdovsey, Syst. u. Morph. 1884, p. 41. 

 Enehytraeus (Archienehsrtraeus) nervosus, Vaillant, Annel^s, p. 386. 

 Pachydrilus nervosus, Michaelsen, JB. Wiss. Anst. Hamb. 1888, p, 58. 

 Definition. Length, i^mm.j setae, 4-7 per bundle. Brain concave in front; outgrowths of 

 nerve-chord large and lobed. Spermathecae with distinct demarcation between pouch and 

 dzict. Hab. — Nova Zembla. 



