390 
CLASS ARACHNIDA. 
biated cleft, as in the Micrommata argelas ; sometimes it is 
sheltered by a prolonged operculum, and terminated like a 
tail, as in the Epeira diadema ; or it sometimes presents itself 
in the form of a tubercle. 
With respect to the simple eyes, the same observer remarks, 
that they shine in darkness, or dusk, like those of the cat, and 
that the arane'ides have probably the faculty of seeing both 
by day and night. 
The abdomen of the arane'ides putrifies and changes after 
death to such a degree, that its colours and even its form be- 
come undistinguisliable. M. Dufourhas succeeded, by means 
of a very prompt desiccation, of which he explains the process, 
in remedying this inconvenience. 
According to Reaumur, the silk undergoes a first elabora- 
tion in two small reservoirs, having the figure of a Rupert’s 
drop, placed obliquely one on each side, at the basis of six 
other reservoirs, shaped like intestines, situated one at the side 
of the other, bent six or seven times, setting out a little below 
the origin of the belly, and leading to the nipples by a very 
slender thread. It is in these last vessels that the silk acquires 
more consistence and the other qualities which are peculiar 
to it. They communicate with the preceding by branches, 
forming a great number of bends, and then divers interfacings. 
On proceeding from the nipples, the silken threads are glutin- 
ous ; a certain degree of desiccation or evaporation of moisture 
is necessary before they can be employed. But it appears, 
that when the temperature is propitious an instant is sufficient, 
since these animals make use of them almost immediately as 
they escape from their spinnerets. Those white and silky 
flakes which we see flying about in spring and autumn, on 
days in which there has been a fog, and which are vulgarly 
termed “ the virgin'' s threads are certainly produced, as we 
have been convinced by following them from their point of 
departure, bv divers young arane'ides, and especially by Epeirae 
