203 



3- Studies on the penial bulb in fourteen species distributed 

 among* five genera have shown the writer that in this material its 

 structure is uniform, in the specimens of a given species, and that it 

 seems to furnish characters of taxonomic importance. Eisen's classi- 

 fication of the subfamilies and genera based on the characters of this 

 organ is, however, faulty. In Marioiiiua provision must be made in 

 the definition for the occasional presence of an accessory gland in 

 connection with \he penial bulb. The stability of the subfamily 

 Bnchytrcriu(u is very uncertain, since it contains only one genus, 

 Unchytrccus, which is now known to contain a few species in which 

 the penial bulb is of the lumbricillid type, species which have the 

 enchytraeid type of penial bulb, and species which have transitional 

 forms of the bulb connecting the regular types. Alterations must 

 be made in Eisen's characterization of the bulb in the genus Fvidericia 

 to provide for wider variation in the number of sets of cells in this 

 organ. 



4. Stephenson has recently described species which have char- 

 acters transitional between Lnmbricillus and Enchytrmis. Additional 

 evidence of the close relation of these two genera is now offered, 

 since it is shown that the penial bulb of the latter shows distinct 

 transitions between the enchytrcTid type and the luml^ricillid type. 

 These two genera were formerly regarded as standing far apart. 



5. The remainder of the summary refers to a single species, 

 LumhricUhis rutihis n. sp. This enchytraeid occurs in abundance in 

 the sprinkling filters of the Chicago Sewage Testing Station during 

 the warm months of the year. Its distribution in the various tanks 

 and filters depends chiefly upon the dissolved oxygen content, the 

 hydrogen sulphide content, and the "freshness" of the influent. It 

 was found associated with numbers of other species of animals, of 

 which the following are the most common: Prorhynchiis sp., Nciiia- 

 toda, Pristina sp., Xais sp., HclodrUiis suhndnciindus, Collciid^ola 

 (Isoto)iia sp.), larva? and pup?s of Psyclioda alhiniacidata and 

 ChironomidcB, and water-mites. 



Its sole mode of progression is by crawling, rough moist surfaces 

 favoring dispersion and dry ones constituting an important hindrance 

 to it. There is no evidence of an ability to swim. 



These worms are sensitive to light and show a decidedly negative 

 response to it. 



Exposure to dry conditions results fatally within a short time — ■ 

 usually less than five minutes. 



These worms are positively thigmotactic, showing a distinct ten- 

 dency to accumulate in masses and to orient themselves in such a way 



