1g10.] J. STEPHENSON: Aguatic Oligocheta of the Punjab. 75 
(a) the ventral sete are throughout the genus longer in seg- 
ments ii-v than in the rest of the body ; 
(b) the alimentary tube is dilated to form a stomach ; 
(c) the nephridia begin in the sixth segment; 
to which may be added— 
(d) the genus does not possess coelomic corpuscles (Bousfield 
[4]); but it seems nevertheless (Beddard [1]) that these 
are present in D. vaga, from which, however, the ptes- 
ent form is far removed. 
With regard to the length of the ventral sete, I have pre- 
viously stated that in the present forms, those of the anterior seg- 
ments are slightly longer than those of the posterior ; but even this 
difference is gradual, not abrupt after the fifth segment ; nor in any 
case is its magnitude such that it could be used as a diagnostic 
character (cf. figures for length of various sete, p. 73, ant.). 
As regards a stomachal dilatation of the alimentary tube, this 
is stated [7] to be not well marked in D. schmardatz. 
I have not seen any account of a species of Devo in which, as 
in the present form, the nephridia begin in the seventh segment. 
Lastly, the character mentioned under (d) above is not an 
absolute distinction between the other species of the genus and the 
present one; since, as mentioned, coelomic corpuscles are present 
in D. vaga, and may be absent in the present form. 
A list of six or seven characters which distinguish this form 
from its nearest neighbour, especially when four of these are pecu- 
liar, or almost peculiar, to the present form alone, might perhaps 
be held as a sufficient warrant for the erection of a new species. 
The species of the genus Devo are, however, variable in a high 
degree: this is illustrated in the present form by the variations re- 
corded in the branchiz, vascular commissures, ccelomic corpuscles 
and nephridia. Michaelsen, discussing this variability [6], alludes 
to the possible advisability of uniting all (European) species under 
two heads, digitata, without palps, and furcata, with palps. In 
such a case the present form would be included in D. furcata, which 
is, as we have seen, at any rate its nearest ally. 
On reading Bousfield’s paper already referred to, which I was 
only able to do after my examination of the worms had been com- 
pleted, I was a little disconcerted as to the value of my obser- 
vations by finding that, according to that author, ‘‘ It is almost 
impossible to determine the species of any given example when 
ordinary methods, such as the compressorium or the live-trough, 
ate alone employed;’’ the reason given being that, in the case of 
the compressorium, the full expansion of the branchial area, which 
is absolutely necessary for exact observation, is prevented. I do 
not however now think that a thin cover-glass would so greatly 
reduce the length of palps and gills as to explain the great difference 
between his figures and mine, and I observe that Michaelsen [6], 
[7], [8] has lately described new species from preserved material. 
Since, however, my acquaintance with the genus is limited to 
