certain Species of Auolosoma. 263 
is confined to the terms used by the authors in their several 
descriptions. 
I can confirm the statement of Vejdovsky that there is no 
nucleus in the cells containing the coloured oil-globules; so 
far this species agrees with olosoma Headleyi and differs 
from Aolosoma tenebrarum, where a nucleus appears to be 
invariably present in the fully mature cell. 
I refer the present species to dolosoma quaternartum on 
account of the fact that there are no nephridia in the cesopha- 
geal segment ; they begin, in fact, in the second seta-bearing 
segment. But I cannot agree with Vejdovsky (doc. eit. p. 20) 
that the pigment-spots are less numerous upon the prostomium 
than elsewhere ; I find considerable variation in this parti- 
cular, but in many specimens—I rather think in the majority 
—the oil-globules were quite crowded in the lateral regions of 
the prostomium. 
I have just mentioned the fact that the oil-globules of this 
- species, like those of Wolosoma Headley and unlike those of 
Holosoma tenebrarum, are not surrounded by any cell-proto- 
plasm or nucleus, except of course when they are just 
beginning to be formed; correlated with this is the fact that 
on treatment with iodine solution there is no deposition of 
black granules around the coloured oil-globules ; this might 
perhaps be expected to occur in the periphery of the smaller 
oil-globules, but it does not. ‘The absence therefore of this 
reaction, which is so characteristic of olosoma tenebrarum, 
may perhaps not necessarily indicate a profound difference in 
the pigment of the three species, dolosoma quaternarium, 
variegatum, and Headley, as compared with Avolosoma tene- 
brarum. If the explanation which I offered in my paper 
upon Aolosoma tenebrarum (Proc. Zool. Soc. 1889, p. 53) 
of the black stain produced by iodine be correct, viz. that it 
is a precipitation of elemental iodine caused in some way by 
the coloured oil-globule, it is perhaps a little difficult to see 
why the supposed influence of the coloured oil-drop in olo- 
soma quaternartum does not reach the cells immediately sur- 
rounding it with which the oil-globule is so nearly in contact. 
This theory may of course be wrong; but in the meantime 
it seems to me to be on the whole more probable that there is 
so far a difference between the several pigments, and that the 
orange-brown pigment of M#olosoma quaternarium and the 
bright green pigment of Aolosoma variegatum and Headleyt 
may be less perfect as respiratory pigments, and therefore 
in course of degeneration. In this connexion it is interesting 
to note that olosoma tenebrarum is on a decidedly higher 
level of organization than any-of the other species at present 
