16 TUBIFEX RIVULORUM. 



ever, on the subject are those of Bonnet,* Jules d'Udekem,t and 

 Edouard Claparede,:j: on the Continent ; whilst at home we have 

 observations by W. C. Mcintosh || and Ray Lankester.§ Bon- 

 net's work deals with the result of cutting the worm in half. 

 Jules d'Udekem gives us a most elaborate and careful monograph, 

 illustrated with four beautifully executed plates ; and he was ably 

 followed by Claparede, whose work refers to a closely allied 

 species, Tiibifex Bo7meii. He points out several errors which 

 d'Udekem had made, at the same time fully acknowledging the 

 general excellence of his work. The works of the two last-named 

 authors are devoted to special points on which they differed from, 

 or made advances on, their predecessors. 



The most abundant worm in Thames mud is Tiihifex 

 rividontm. Two other worms are, however, very abundant, 

 living inextricably mixed with it in masses : one is Limnodrihis 

 Udekemiaims of Claparede, distinguished by the absence of the 

 capillary setae of the former, and by the unusual thickness of the 

 integument; and the other, Tubifex umbeUifer of Lankester, 

 which has the dorsal setae of the first ten segments webbed (see 

 PI. I, Fig. i). My own observations have been confined to T. 

 rivuloriim. 



The worm (Fig. 7) is about an inch or a little more in length, 

 and from its small size, and the transparency of the integument, 

 forms a good subject for examination in the living state with 

 low powers of the microscope : the chief features of anneli- 

 dan organisation revealed thereby being the perivisceral cavity, 

 with its contained perivisceral fluid and corpuscles (Fig. 10), 

 — the system of closed vessels containing a coloured non-cor- 

 pusculated circulating fluid, regarded by some authors as a true 

 blood system, and by others as a pseudo-haemal system analagous 

 to the water- vascular system of the Scolecida, Rotifera, etc., the 

 nature of which is respiratory (Figs. 9 and 10); — and lastly, 

 the intestine with its covering of glandular hepatic cells (Fig. 10). 

 The reproductive organs, extending from the 9th to the 15th 

 segment, are only indicated, on a casual glance, by the superior 

 size of this part of the body in mature specimens, and require 



* (Euvres d'histoire naturelle cle C. Bonnet, Amsterdam, torn. I., 1780. 



t Histoire naturelle du Tubifex des ruisseaux : Memoires couronn^s de 

 I'Academie des Sciences, de Belgique. Brussels, 1855. 



Memoires 



de 



X Recherches Anatomiques sur les Oligoch^tes, par Ed. Claparede, 

 la Soci^te de Physique de Geneve, tome XVI., 1861. 



II On some points in the structure of Tubifex, by W. C. Mcintosh, M.D. 

 Transactions Edinburgh Society, Vol. 26, 1870. 



§ Observations on the Organization of Oligochcetous Annelids, by Ray 

 Lankester: Annals. Nat. Hist., 1871 ; also, on the Spermataphores of Tubifex, 

 Quar. Journ. Micro. Science, 1871, p. 180. 



