170 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



HELODRILUS (BIMASTUS) TUMIDUS (Eisen). 



Allolobophora tumida Eisen. 1874a: 45. 



Allolobophora (Bimastus) tumida Michaelsen, 1900: 10. 



Eelodrilus (Bimastus) tumidu^ Michaelsen, 1900a.- 502. 



Length, about 3 cm. Somites, 40-50. Color, reddish-brown. 

 Prostomium, epilobic f. Setae, closely paired. Clitellum on 

 22-29.' Tuberciila pubertatis on 27 and 28; inconspicuous. Sper- 

 miducal pores on 15, with small but definite glandular elevations. 



The description of this species by Eisen is in substance as above 

 and is accompanied by four figures (1874a, fig. 5-8) showing, respec- 

 tively: The dorsal aspect of the worm, natural size; ventral aspect of 

 the chteUar region with the tubercular pubertatis; an outline sketch 

 showing the shape of the body in cross section and the relations of the 

 setae; and a drawing of the superficial aspects of the posterior two 

 somites. 



One specimen of the original collection was presented by Eisen 

 to the United States National Museum, and has given an oppor- 

 tunity to study the internal anatomy and to make comparisons with 

 closely related species. There is no indication of the number of 

 specimens collected. In some respects the correspondence of Eisen' s 

 figures and description with the museum specimen is so close that it 

 seems fairly probable that they were based, at least in part, on that 

 particular worm. 



The specimen is strongly contracted and measures 1.8 cm. in length. 

 Eisen's figure (natural size) shows a length of 2 cm. His statement 

 ''longitudo circiter 30 mm." was probably based on living specimens. 

 The maximum diameter is .25 cm. The number of somites is 48, 

 while Eisen gives ''circiter 40" in his description and 50 in his table 

 which lists characters of several species. The appearance of the 

 specimen suggests the probability that it is incomplete; and this may 

 account for the fact to which he calls attention — namely, that toward 

 the posterior, from and including the chtellum, the somites gradually 

 increase m length up to the last somite, which is almost twice as long 

 as the one next preceding. It seems to me fairly probable that the 

 last somite is really just at the beginning of regeneration of more 

 somites, but I have no positive evidence to that effect. 



The setae are closely paired, but the intervals are not as figured by 

 Eisen. On somite ^2, aa:ab:'bc:cd:dd=ld>-A:\^A-Ab represents very 

 closely the relative setal distances. Toward the posterior, dd becomes 

 less and ab and cd slightly greater, but nowhere is ab as small as 

 figured by Eisen, who represents it as distinctly less than cd and only 

 about \ aa. Neither is dd as small as represented in the figure, 

 where it is scarcely f aa. In the specimen examined, dd is at least 

 2 aa and near the clitellum is about | aa. 



