268 Transactions of the Society. 



already laid are all the better for being fairly broad, as we see when 

 we take a glance at the genus Limnodrilus, for example, which 

 contained only three European species when Yejdovsky published 

 his System und Morphologie in 1884, but now consists of some- 

 thing like twenty well-defined species. 



In order to show how easily confusion may arise in identifying 

 these Annelids, it may be well to give a few typical gleanings from 

 different parts of the country. I take the entries at random from 

 my note -books. 



1. A pool near Smisby, Ashby-de-la-Zouch : — Tuhifex (= Ili/o- 

 drilus) camimnulatus Eisen ; Limnodrilus painllosus Friend ; L. 

 aurostriatus Southern ; L. aurantiacus Friend ; L. nervosus Friend ; 

 Tuhifex honneti Claparede. No fewer than five distinct species in a 

 little mud brought away in a 2-oz. bottle. 



2. A ditch at Newark, October 13, 1911 :— Tuhifex {= Ilyo- 

 drilus) campanulatus Eisen ; Limnodrilus hoffmeistcri Clap. ; L. 

 ■painllosus Friend ; Tlyodrilus rohustus Friend. 



3. A gutter running into the Trent at Gunthorpe, Notts, 

 November 8, 1911: — Tuhifex tuhifex 0. F. Miiller ; Limnodrilus 

 impillosus Friend ; Llyodrilus rohustus Friend. 



4. The River Thames at Tower Bridge, collected for me by Mr. 

 C. S. Todd, of Tottenham, September 30, 1911 ■.—Limnodrilus hoff- 

 meisteri Clap. ; Monopylephorus tricliochMns Dit, ; Tuhifex tuhifex 

 0. F. Miiller ; Limnodrilus longus Bretscher ; Fsammoryctes har- 

 hatus Grube ; Limnodrilus papillosus Friend. 



5. Banks of a stream at Netherhall, in Derbyshire, Novem- 

 ber 16, 1911 : — Bhyacodrilus falciformis Bretscher ; Tuhifex tuhifex 

 0. F. Miiller ; llyodrilus rohustus Friend ; Limnodrilus papillosus 

 Friend. 



Two things should here be noted. First, that no mention is 

 made of such worms as Paranais, Marionina, Pachydrilus, Nais, or 

 Stylaria, which at first sight closely resemble most of the Tubificids. 

 And, secondly, that the lists represent minimum gleanings, and are 

 not in any way to be regarded as exhaustive. 



II. — Descriptive. 



While the bulk of the generic names which have been devised 

 for members of tlds family, such as Tuhifex, Limnodrilus, or llyo- 

 drilus, throw no light on the structure of the Annelids, a few have 

 been selected with a view to helping us in that direction. Bran- 

 cliiura, Monopylephorus, and Bothrioneuron tell of processes on the 

 tail and other points of interest. But they also land us in difficulty 

 when we find a Branchiura without branchiae, and a Monopylephorus 

 which has paired organs instead of unpaired. Evidently something 

 is wrong here. 



All kinds of organs have been seized upon by systematists in 

 order to secure some satisfactory method of arrangement. One has 



