248 



ELLIOT ROWLAND DOWNING. 



These observations are directly antagonistic to those of other 

 investigators on several points .of anatomical detail and of func- 

 tion of some of the vessels. I have given above a statement of 

 the general arrangement of the branching afferent vessels with 

 reference to the nephridia ; it will be evident from text-figure 2 

 that my results only agree in a general way with the statements 



FIG. 2. Diagrams of the blood vessels supplying the nephridia in the several 

 species of Arenicola, a, A. Clafaredii, b, A. cristtita, c, A. marina, ti, A. Grubii ; 

 d will also serve as a diagram of the blood vessels of A. ecaudata. The form of the 

 nephridia and of the digestive organs in the latter species, would be somewhat differ- 

 ent but the arrangement of the blood vessels is the same as in A. Grubii. The dorsal 



vessel is shown by a solid line, thus . Afferent vessels arising from the ventral 



vessel are shown in broken lines, . . . Efferent vessels connecting with the 



sub-intestinal blood vessel are shown in dotted lines, D. J-'., dorsal vessel. 



j\ r .L. V. t nephridial longitudinal vessel. P. V., parietal blood vessel. 



of previous authors. Thus in all nephridia of A. Claparedii, in 

 some of A. marina and occasionally in A. Grubii, the afferent 

 branch of the ventral vessel enters the apex of the funnel before it 

 branches. In A. cristata one finds frequently, particularly in the 

 somites containing the second and third nephridia. that the affer- 



