British TvMjicidm. By Rev. H. Friend. 285 



I have been familiar with various species of Ilyodrilus for many 

 years, it is only during the last few montl)s that I have been able to 

 bring anything like order out of the prevailing chaos. Eisen him- 

 self placed certain species of Ilyodrilus under the genus Tuhifex — 

 owing to his never having seen the latter. I have reason to believe 

 that several species yet remain to be described. As the American 

 and European genera are still chaotic, I give the generic characters 

 for the species at present known for Great Britain. 



VI. Genus Ilyodrilus (Eisen and Stole revised). 



Tubificid Annelids possessing two kinds of setse, viz. capilli- 

 form and forked. The capilliform setse limited to dorsal bundles ; 

 forked setee dorsal and ventral, either alike or slightly different. 

 Sometimes the anterior differ from the posterior bundles both in 

 number and size. Spermathecse large ; spermatophores present in 

 perfectly adult specimens. Efferent duct long or short, with pros- 

 tate, atrium, and round penis-sheath. 



This definition is a temporary expedient to meet the needs of 

 British research. Eevision will be needed when these researches 

 are more complete. 



1. Ilyodrilus cartvpanulatus Eisen. 



Brain longer than broad, narrowing posteriorly, with deep, 

 narrow concavity. Penis broadest at middle ; penis-sheath bell- 

 shaped. Length of oviduct half that of penis. Spermatheca bent 

 in the shape of an S, enlarged and sac-shaped. Setse : two kinds 

 always present, viz. hair spines and forked spines. The two prongs 

 (or teeth) of the latter nearly equal, diverging at less than a right 

 angle. 



Hahitat. — Europe, Sweden, Chris tianstad. 



1885. — Eisen, Oligochsetological Eesearches, p. 893, plate viii. 

 fig. 7, ft, h, e, d, as Tnhifcr camjjanulatits. 



One of the commonest and most widely distributed of our British 

 Tubificids ; often confused with Tuhifc.r. My first unmistakable 

 record is dated " Bolton Leegate, Cumberland, April 9, 1896." Here 

 are my original notes. " Tubificid found in mud in a little runnel 

 by the Church. About ^ or | in. in length, coiling up and shun- 

 ning observation. Bright red blood. Capilliform and forked setse ; 

 girdle and chitinous penes. Cap. setae 2-4 in front segments, 1 from 

 about the 10th segment Ijack wards. Coiled tube connected with 

 egg-sac going back 3 or 4 segments behind the girdle. Dark chlora- 

 gogen cells begin behind segment 5 (i.e. in front of segment 6). 

 Dilating heart in 8. Tlie worm very delicate and transparent. 

 Sette present in girdle segment near the penes." A sketch of the 

 penis-sheath, which is campanulate, is given in my note-book. 



