352 OLIGOCHAETA 



notopodia and neuropodia of the Polychaetes ; but it does not 

 seem certain that this comparison is justifiable. It was at one 

 time thought that the continuous circle of chaetae of the Peri- 

 chaetidae was the primitive condition ; but Professor Bourne has 

 lately found that in Perichaeta the young embryos have not got 

 this continuous circle ; it is only acquired later. 



Branchiae. The Oligochaeta were called by Cuvier the 

 " Annelides abranches setigeres." But the epithet " abranches " 

 is now known to be inaccurate. In fact it really was so when 

 Cuvier wrote ; for naturalists were at that time well acquainted, 

 chiefly through the elaborate work of 0. P. Miiller, with the 

 little fresh-water Naid Dero, the posterior extremity of which is 

 provided with a varying number of branchial processes. These 

 are furnished with looped blood-vessels and are covered exter- 

 nally by cilia, so that the water containing oxygen is constantly 

 renovated. The second instance of a gilled Oligochaete was 

 discovered in the very same family. Professor Bourne 1 of Madras 

 found in " tanks " a Naid which he named Chaetobranchus, in 

 which the head segments, to the number of fifty or so, are 

 provided with long ciliated processes, which as a rule enclose 

 the dorsal chaetae of their segments, and in addition a capillary 

 loop. Curiously enough, this very same worm made its appear- 

 ance in the Victoria regia tank at the Botanical G-ardens in the 

 Begent's Park, whither it had in all probability been accidentally 

 imported. Two members of the family Tubincidae were the next 

 examples of gilled Oligochaeta made known to science ; one 

 of these, Branchiura sowerbyi, 2 appeared also in the Botanical 

 Gardens, so that its native home is unknown. It differs 

 from Chaetobranchus in that the gills are at the posterior 

 end of the body, and are contractile ; during the life of the 

 worm they are in continual motion. A species of the South 

 American genus Hesperodrilus? H. branchiatus, is also gilled, 

 and, so far as can be made out from a spirit-preserved specimen, 

 the gills are precisely of the same pattern and contractility as 

 those of its ally Branchiura. Possibly Branchiura ought to 

 be included in the same genus with Ifespei*odrilus. A worm 

 which, was originally described by Grube as Alma nilotica, 

 should really have been placed before the three last-mentioned 



1 Quart. J. Micr. Set. xxxi. 1890, p. 83. 2 Beddard, Ibid, xxxiii. 1892, p. 325. 

 3 Beddard, Ann. Mag. Nat. Hist. (6) xiii. 1894, p. 205. 



