1g10.] J. STEPHENSON: Aquatic Oligochata of the Punjab, 65 
conclude that we have here a collection of morphological resem- 
blances which are comparatively unimportant from a physiological 
standpoint, and which it is in the highest degree improbable 
should have arisen independently. . 
Admitting then the close connection of the two forms, is it pos- 
sible to unite them in the same genus? Most of the differences 
between the two are obviously of only specific value; such are 
the greater extension posteriorly of the branchial processes in the 
present form; the absence of sickle-shaped sete in the dorsal 
bundles, and of any difference between the anterior and posterior 
setzee in the ventral bundles; the colourless character of the 
coelomic corpuscles; and, possibly, the pulsation of the anterior 
lateral vascular loops and the ciliation of the general body-surface, 
which two last characters do not appear to have been observed in 
Branchtodrilus. 
The difference in the anterior limit of the dorsal setal bundles 
(and branchial processes) belongs, however, to a different category. 
Such a feature has generally been held to be of generic and not 
merely specific value. Thus the presence of dorsal setz on all seg- 
ments from the second onwards is mentioned as a feature in the 
generic diagnosis of Branchiodrilus in Bourne’s original paper [2], 
in Beddard’s Monograph of the Oligocheeta [1], and by Michaelsen 
[5]; a similar feature is the chief, if not the only, generic distinc- 
tion between Naidium and Nais; Beddard ([1], p. 281), merging 
together a number of genera of other authors under the one name 
Nats, does so largely because they ‘‘ agree in the important fact 
that the first five segments are cephalized,—that the dorsal setze 
do not commence until the sixth segment,’’ and by implication 
would exclude from the genus any form which did not show this 
cephalization. Similarly Pristina and Natdium are united by him 
on the ground of the absence of this feature. Bourne [3] also 
believed that the number of cephalized segments is constant for 
the genus, and thought it probable that Dero furcata, possessing 
four acheetous dorsal segments, should on this account be removed 
from the genus, since the other members of it have five such 
segments.! 
It seems necessary, therefore, to erect for the present form a 
new genus, for which I suggest the name Lahorta, with hortensis 
as a specific distinction. I believe notwithstanding, on the ground 
of the similarity of distribution of the branchial processes and of 
their relations to the setz in the two forms, that the connection 
between the present form and Branchiodrilus is a close one; and if 
this be admitted, it is perhaps worth while asking whether a 
cephalization which affects only the setal distribution (for the 
absence of gills on segments ii-v of the present form is evidently 
correlated with the absence of the setee which are necessary to 
1 On the other hand Michaelsen [5] unitesinto one genus Pavanais the 
Naidium naidina of Bretscher, Pavanais littovalis of Czerniavsky, and Uncinais 
(Ophidonais) uncinata of Levinsen, though their dorsal sete begin respectively on 
the second, fifth and sixth segments. 
