280 Transactions of the Socidy. 



also durch zwei Segmente. Der Darin beginnt in 6. Blut rot 

 in alien Segmenten bis 11 tritt je am hintern Dissepiment eine ein- 

 fache, lange, pulsirende Gefassschleife vom Etickengefass aus. 

 Eigentliche Seitenherzen fehlen. Lymphkorper kugelig, dicht und 

 grob granulirt. 



" Gehirn hinten in zwei lange Lappen ausgezogen, mit breitem 

 Zwischenraum an deren Grande (fig. 5). Spermatheken in 9, 

 1 I'aar; kurze, breite Sacke mit breiter Oeffnung. Grosse Eier 

 bis in 11. Hoden und Ovarien nicht beobachtet. Fundort : 

 Fiirstenalp, Bach und Brunnentrog." 



Bretscher places this, without note or question, among the 

 Tubificidaj ; though one might have expected attention to be drawn 

 to the anomalies. In 1903 (Kevue Suisse de Zool. xi. p. 13) the 

 author tells us that he had given a description of the species two 

 years before, and adds that the spermathecse (which he illustrates) 

 are pear-shaped or round, with a wide slit-like aperture. The pro- 

 state is somewhat club-shaped (as figured), about four times as long 

 as it is broad, and glandular. He adds that the creature seems to 

 belong exclusively to the Bachfauna, but is not so much an inhabi- 

 tant of the water as of the moist earth. 



In 1904 Ditlevsen (Zeitschr. Wiss. Zool. Ixxvii. p. 408) described 

 the same Annelid as Ilyodrilus filiformis sp. n. ; though he was not 

 unfamiliar with Bretscher's work. His description sets forth the 

 following points : — The setffi are all forked, the ventral agreeing 

 with the dorsal, but somewhat stronger, the upper tooth larger than 

 the under {d fig. 5 in original), and numbering four dorsally with 

 five to seven ventrally in each bundle. Nephridia swollen in front 

 of the septum {a fig. 3). Vas deferens {vd A fig. 4) long and 

 narrow, very difficult to follow ; sac -formed atrium clothed with 

 glands. Genital setas present, having the form of a large spoon or 

 ladle (die Form eines grossen Loffels). Spermathecse with small 

 receptacle, which is probably filled with spermatozoa rather than 

 with spermatophores. 



The description given by Bretscher differs in certain details 

 from that which I drew up on finding the worm in Derbyshire 

 under the title Meganymflia iJachydriloides g. et sp. n. Ditlevsen, 

 in spite of his shrewd allusion to the spermathecse, and his conten- 

 tion that the genus belongs rather to the ISTaididae than to the 

 Tubificidse, is in error in referring this species to Ilyodrilus, whether 

 it be that of Eisen or of Stole. I shall have to deal with Ilyo- 

 drilus, however, later. It must, therefore, suffice for the present 

 to draw attention to the work of Bretscher and Ditlevsen, and 

 proceed to the study of Bhyacodrilus as found in this country. 



When I first discovered it in the summer of 1911 embedded in 

 mud by the side of a little Derbyshire stream, the first thing that 

 struck me was its resemblance to Pachydrilus or Marionina when 

 seen by the naked eye. The moment it was placed under the 



