Ig16. | J. StepHENSON : Indian Oligochaeta. 305 
expanded these appear merely as a fold of the margin 
(cf. Stephenson, 24). 
(2) The single specimen from Khed, referred to above, in which 
the anterior of the three pairs of gills are continuous 
with the margin of the funnel. 
(3) The specimen figured (fig. 3), where one of this pair is well 
within the margin. 
(4) The bulk of the specimens from Khed, with three pairs of 
true gills (¢.e. all separate from and within the margin). 
(5) The Bombay specimens, similar to the last, the dorsal 
margin of the funnel not gill-like. 
(6) The single specimen from Bombay, with three pairs ot 
gills, and projections of the dorsal margin of the funnel. 
(7) Aulophorus stephensoni, described as having four pairs of 
gills, the anterior being the smallest, and forming only 
small projections on the margin; using the recognized 
terms, there are ‘three pairs of true and one pair 
accessory gills. 
(8) Aulophorus palustris, Mchlsu. (11, 22) possessing four pairs 
of gills, all within the margin of the funnels. 
The series is not in absolute strictness one of increasing com- 
plexity throughout, since the Khed specimens (2, 3 and 4) have a 
somewhat projecting and indented dorsal margin, while this is 
quite straight in 5. But it does show in a striking manner the 
evolution of successive pairs of gills as differentiations of the 
margin of the anal funnel. 
I think it will be admitted that, with the exception of number 
8, the difference between the arrangements of the gills in successive 
terms is nowhere sufficient to allow us to separate the successive 
terms as different species or even varieties. No. 6 is almost identi- 
cal with 7; sois 5 with 6, and moreover comes from the same 
limited batch of material; both 5 and 6 must therefore be united 
with 7. The same reasoning obliges us to unite 2, 3 and 4 with I. 
But 5 is identical with 4, or even slightly less differentiated, since 
it wants the slight bifid projection of the dorsal margin of the fun- 
nel. From a consideration of the characters of the gills, then, we 
must conclude that Aulophorus furcatus, A. stephensont, and all 
intermediate forms constitute a single species. 
I have said ‘‘ from a consideration of the characters of the 
gills.’ The case would be different if we could differentiate the 
terms of the series by means of other structures, —for example the 
setae. I do not think we can. ‘There is a considerable amount of 
variation to be met with amongst these forms. Recent descrip- 
tions of A. furcatus have been given by Piguet (19) and myself (24) ; 
Piguet finds a stomachal dilatation of the gut in segm. viii, which 
was absent in my specimens, and there are slight differences in 
the accounts of the setae. I found that in the Bombay specimens 
the prongs of the posterior ventral setae were as a rule equal in 
length, and the distal was about two-thirds as thick as the proximal ; 
