ö4 DESCRIPTIONS OF EARTHWORMS. 



dorso-iiitegumentary vessel of Bourne) rightly is considered 

 by Perrier himself in Urochaeta to be the homologue of the 

 afferent vessel of the dorsal branchiae in Annelida bran- 

 chiata. Now these branchiae receive always their afferent ves- 

 sel from the dorsal trunc or its commissural vessels , whilst 

 their efferent vessel joins the ventral trunc. In the vicinity 

 of those branchiae there occur often contractile dilatations 

 of the vessels , which of course tend to surmount the greater 

 resistance, caused by the flowing of the blood through 

 the branchiae. While therefore in the majority of Annelids 

 the dorsal vessel is considered to contain venous blood , 

 that flows in the directions of the branchiae , this should 

 according to Perrier a. o. not be the case in Lumhricus , the 

 vascular system of which is constructed on the same pattern." 

 I believe that Vejdowsky, who agrees with my view that 

 the blood flows from the intestinal capillaries into the 

 dorsal vessel, based his opinion upon the same morpho- 

 logical data, for, on p. 117 of his System und Mor- 

 phologic der Oligochaeten , he refers to Alma nilotica , 

 which is furnished with branchiae in the posterior region 

 of the body; this curious Oligochaeta from the banks of 

 the Nile was first mentioned by Grube (Archiv fur Na- 

 turgesch. 1855, p. 129, pi. V, fig. 11 — 15) and later on 

 described by Levinsen under the name of Digitihranchus 

 niloticus (Vidensk. Meddel. naturh. Forening i Kjjzibenhavn , 

 1889, p. 321, pi. VII, fig. 7 and 8). 



EXPLANATION OF PLATE 6. 



Fig. 1. Aniens gigas Perrier; general view of the contents of the body cavity, 

 when the body wall has been cut along the dorsal mid-line : ah. abdo- 

 minal heart; cv. commissural vessel; iv. supra-intestinal vessel; n. ne- 

 phridiam; pii. extra-buccal pepto-nephridiura; vs. vesicula seminalis. 

 X 14 diara. 



Fig. 2. View of the intestinal tract and the setae , after removal of other 

 structures: g. gizzard; gl. intestinal gland; oe. oesophagus. 



Fig. 8. Nephridium of the sixth segment. X 3 diam. 



Fig. 4. a. Ordinary seta; b. elongated seta of the clitellum. X 25 diara. 



Notes from the Leyden jMuseum , "Vol. XIII. 



