402 General Notes. [ April, 
tinguished by a black oval dot; just as in other larve with 
tracheal gills, as described by Palmén, the stigmatic branches are 
completely closed. The larvæ are ordinarily found attached to 
stones, and are rather more frequent in stagnant than in running 
water. They form for themselves a chamber with delicate but 
closely spun walls, and they do not leave this, as a rule, until they 
attain to the imaginal state. The spaces at the edge of the co- 
coon only serve asa means of exit for the fæces ; they live on 
the diatoms and other cellular Algæ which grow on the stones to 
which they attach themselves. They almost always fix themselves 
by their backs to the stones, and in correlation with this we ob- 
serve that they present the remarkable condition of having their 
dorsal surface pale, and their ventral dark. This is not however, 
to be regarded as a protective adaptation, but as the result of an 
earlier condition in which the whole of the larva was darkly pig- 
mented; the paleness of the back is due to the want of light. 
After an account of the pupa and of the homes in which it 
dwells, the author passes to some other species of the same genus, 
all of which are Brazilian. These are much less common, an 
their specific characters are not yet fully worked out, but there are 
probably five species. The gills, which are always unbranched, 
never attain to the relative length seen in C. pyropalis, but they are 
always more numerous. The covering of the pupa contains air- 
spaces in its outer division, which are connected with that of the 
inner, but as the stones or alge forbid any exchange of gas with 
the exterior, this can only be effected by the spaces in which the 
water is able to pass; this explains how it is that we sometimes 
find the air-chambers on the side of the house which is attached 
to the stone. : 
ORGANS OF HEARING AND SMELL IN SPIDERS.—F. Dahl pro- 
poses to classify spiders according to the charac ter and disposition 
of the auditory hairs on the limbs of these animals, as follows : 
1, Tibia with two series of auditory hairs, metatarsus with one 
hair, and tarsus with a rudimentary pit or depression free from 
hairs, e. g. Epeiridz, Uloboride, Theridiidz, and Pholeide. 
2. Tarsus with no rudimentary depression for auditory hairs, 
usually bearing a number of hairs like the metatarsus and tibia, 
e. g. Territelariz, Dysderide. 
The remaining number of this class are further subdivided ac- 
cording to the presence of one or two series of auditory hairs on 
the tarsus. A single series is characteristic of Amaurobiide, 
 Agalenidæ, Philodromide, Thomisidz, and Attide. Two series 
_ occur in Drasside, Anyphoenide and Lycoside. 
= _ Dahl has satisfied himself that these auditory organs can appre- 
=~ €late not only sound, but also variations of atmospheric pressure, 
f 
ich 
= An olfactory org is stated to exist on the maxilla. On the 
=- surface in front of which the mandibles work to and fro is a soft 
* 
