276 Linnean Society. 
it being little if any more than is due to the laceration and com- 
pression which the injured part has sustained. 
Under the second head, the observations were made on a male 
and female of Tegenaria civilis; on two females of Segestria senocu- 
lata; twice on females of Ciniflo atrox and females of Lycosa agretica ; 
on a female Hpeira Diadema and a female Celotes sazatilis; on two 
females of Epeira Diadema ; and lastly on a female of Epeira Diadema, 
which in a state of high exasperation bit itself. Extensive mechani- 
cal injuries,-Mr. Blackwall states, commonly prove fatal to spiders, 
whether received in conflicts with their congeners or otherwise ; but 
no evidence supplied by his experiments indicates that the fluid 
emitted from the orifice in the fangs of the Araneidea possesses a 
property destructive to the existence of animals of that order when 
transmitted into a recent wound. 
Thirdly, as the result of numerous experiments on insects, made 
with Epeira Diadema, Segestria senoculata, Epeira quadrata, Tegenqria 
civilis, and Agelena labyrinthica, the author comes to the conclusion 
that they do not present any facts which appear to sanction the 
opinion that insects are deprived of life with much greater celerity 
when pierced by the fangs of spiders than when lacerated mechani- 
cally to an equal extent by other means. It is true however that 
the catastrophe is greatly accelerated if the spiders maintain a pro- 
tracted hold of their victims, but this is obviously attributable to the 
extraction of their fluids, which are transferred by often-repeated 
acts of deglutition into the stomachs of their adversaries. 
Fourthly, in his experiments on inanimate substances, Mr. Black- 
wall found that litmus-paper presented to spiders belonging to several 
genera when in a state of extreme irritation, and moistened by the 
transparent fluid which issues under such circumstances from the 
fissure near the extremity of their fangs, invariably became red as 
far as the fluid spread, clearly proving that this secretion, although 
tasteless, is an acid. On the other hand, the fluid which flows from 
the mouth, as also that contained in the stomach and that which is 
discharged from wounds inflicted on the body or limbs, were found 
by the same chemical test to be alkaline. ‘Turmeric paper was ren- 
dered brown by the application of the fluids from the mouth and 
stomach, and restored to its original colour by the agency of the 
fluid secreted by the so-called poison-gland, thus affording complete 
confirmation of the respectively alkaline and acid natures of these 
several secretions. 
Mr. Blackwall concludes his paper by proposing the name of 
falces for the instruments by which spiders seize and destroy their 
prey ; the term mandibles being obviously improper for organs which 
do not, as Mr. W. 5. MacLeay has plainly shown, constitute any 
part of the oral apparatus ; and that of chelicera, proposed by M. La- 
treille, implying an hypothetical analogy to the antennz of hexapod 
insects, from which they differ so widely both in structure and in 
function. He adds, that he has observed the labrum in a low state 
of development in species belonging to numerous genera, and that 
it is attached by its base to the superior surface of the palate, but 
