296 The Irish Naturalist, [Nov., 



the posterior regions of the body. Dr. Benham did a good 

 deal six years ago b}^ the publication of ** Some Notes on 

 Aquatic Oligochaeta " {After. Jo7ir., vol. xxxiii. n.s., p. 187 et 

 scq.) towards clearing up difficultiCvS, and making this subject 

 more lucid ; and since then our knowledge has yearly been 

 growing more definite and satisfactory. 



In addition to these external characteristics we have also 

 the arrangement of the blood-vessels ; the nature and position 

 of various organs concerned in the processes of reproduction ; 

 and the presence, in certain members, of peculiar chitinous 

 tubes, varying in length and shape with the genus or species, 

 and affording in some cases the readiest means of identifica- 

 tion or distinction. 



Of the various genera belonging to the family TubificidcB, 

 the following are all which are at present known to occur in 

 Ireland: — Tiibifex, Limnodriltis, HeterochcBta, Psammorydes 

 and Hcmiticbifex. Respecting some of these I have already 

 written in these pages from time to time, but I think it will be 

 well in this paper to bring our present knowledge of the Irish 

 Tubificids to a focus, in order that future work may be facili- 

 tated. As the genuine Tubifex has not, so far as I am aware, 

 been placed on record for Ireland since the Annelids have 

 been systematically studied, it may be advisable to give in the 

 first place a brief diagnosis of this typical form. I may take 

 this opportunity of warning collectors who make a study of 

 fresh-water worms against the idea that because one worm in 

 a given collection happens to be the genuine Tubifex, therefore 

 the whole of the gathering is made up of that species. It will 

 be frequently found that three or four different species, 

 representing in some cases as many genera, are collected 

 together in one spot. 



Tubifex rivulorum, Lamarck 

 A slender aquatic womi frequently extending to an inch in length, of 

 a bright-red colour. Very gregarious, living in mud, which it usually 

 makes into tubes into which a portion of the bod}' is thrust. Active, 

 often associated with other species or genera belonging to the same 

 family. Integument very delicate and transparent, enabling the blood- 

 vessels and organs to be clearly seen. Possessed of three kinds of setoe, 

 viz. (i) long, capilliform, or hair-like setee, usually two or more in the 

 dorsal bundles (intermixed with others), from the second segment to 

 the twentieth or thirtieth. The number of segments in which these 



