Mr. J. Wood-Mason on Scolopendrella. 61 
the anterior faces of the leg-bases. If a moribund specimen 
be placed on its side under the microscope, a row of minute 
specks as bright as globules of quicksilver is seen, and re~ 
mains visible until the contractions of the tissues consequent 
on drying have driven all the air from the trachee ; and in 
specimens killed and discoloured by osmic acid, the stigmata, 
with the trachez running from them, are to be seen with the 
greatest distinctness, the latter being marked out by silvery 
streaks due to the presence of air. ‘The tracheal tubes are all 
devoid from their very origin of the spiral thickening of their 
walls, so characteristic of the trachez of insects. Hach of 
the stigmata leads into a tube which passes inwards, back- 
wards, and upwards, slightly increasing in calibre as it goes, 
and meets its fellow of the opposite side in the middle line so 
as to form an arch; at the point where the tubes of opposite 
sides meet one another there is a slight blurriness or break in 
the continuity of the arch; and there is an irregularity in the 
height of the arches, to a certain extent corresponding to the 
irregularity in the length of the terga already noticed. No 
tufts of tubes appear to be given off from the arches; and I 
have not as yet made out in the body any other trachez 
besides these metamerically arranged ones. In the head, how- 
ever, there are certainly trachez present; but I have not yet 
studied them sufficiently to be able to speak confidently about 
their arrangement and distribution. 
The huge “crateriform openings,’”’ considered by Ryder 
to be the stigmata, have nothing whatever to do with the 
respiratory apparatus, the openings of which are excessively 
minute. 
The respiratory apparatus of Scolopendrella consists, then, 
as far as it has yet been made out, of a series of eleven back- 
wardly directed arches, opening by as many pairs of minute 
stigmata on the anterior faces of the leg-bases. If, in addition 
to the posterior arch, each pair of stigmata gave off an anterior 
arch, and every anterior were anastomosed in the middle line 
to a posterior arch, we should have an arrangement precisely 
similar to that which we meet with in the segmentally arranged 
portion of the tracheal system in such a Chilopod as Greophilus, 
in which a similar blurriness is to be seen at the points of 
anastomosis of the anterior and posterior arches. 
? Excretory Apparatus.—Besides the stigmata, there is on 
every pedigerous somite, except certainly the first, and _pos- 
sibly also the second, eleventh, and twelfth, a pair of huge 
two-lipped apertures surrounded by a low circular wall, the 
summit of which is defended by a circiet of movable spines. 
They are in the round sclerites to which the functional legs 
