276 Linnaan 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 Epe'ira Diadema and a female Ccdotes saxatilis ; on two 

 females of Epe'ira Diadema ; and lastly on a female of Epe'ira 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 Epe'ira Diadema, Segestria senoculata, Epe'ira quadrata, Tegenaria 

 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. S. 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 antennae 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 



