June 1, 1SGS.] 



HAKDWICKE'S SCIENCE-GOSSIP. 



129 



taclied to the forepart of the cephalo-thorax by a 

 joint, and have a lateral motion like the jaws of 

 insects. These organs perform somewhat the 

 function of mandibles, and have in fact been so 

 called by some authors, but improperly, for they 

 form no part of the mouth. Their function is to 

 seize and kill the prey, but they do not assist in 

 mastication. 



Fig. 119. Falx, with poison gland attached, a. Fang; 

 J, Poison gland. , 



Fig. 120. Fang magnified, showing exit of poison duct. 

 a. Exit of duct. 



Each falx is composed of two parts, the base and 

 the fang. The base serves simply as the support 

 for the cutting instrument, and has a groove on its 

 under surface, into which the fang is folded down 

 when not in use. The fang is hard, sharp, and 

 sickle-shaped, and is, in the instance we are 

 considering, armed with a row of thirty pointed 

 teeth on each side, and a smaller number on 

 the under surface. Attached to the falces is a 

 highly-interestiug apparatus which is believed 

 materially to assist the spider in the capture 

 of its food. This consists of two glands, com- 

 posed of a number of filaments, united by a mem- 

 brane into the form of a sac ; these are situated in 

 the interspaces of the muscles of the cephalo- 

 thorax, and communicate with the falces by means 

 of a duct. These glands secrete a fluid which is 

 supposed to possess slightly poisonous properties, 

 aud thus aid the spider in the destruction of the 

 insects on which it feeds. 



Stories are told of the poisoned bite of spiders 

 having proved fatal even to man ; these are not, 

 however, supported by very reliable evidence. Cer- 

 tainly no English spider is capable of inflicting a 

 bite sufficiently hard even to pierce the human skin ; 

 this I haja frequently proved by experiment. 



So far as I am aware, no experiments have been 

 made to prove the directly poisonous properties of 

 this secretion. Any such experiments are, in the 

 case of our British spiders, surrounded with great 

 difficulties. Speaking for myself, I may say that 



some I have made in reference to this question have 

 been only in a measure satisfactory, but such as 

 they were they rather tended to prove that this 

 fluid does possess some properties fatal to insect 

 life. The exact position in the fang of the orifice 

 through which this fluid exudes has long been a 

 question of dispute. Very recently a discussion 

 took place on the point in the pages of this journal. 



Fig. 121. Mouth, a a, Maxilla?; b, Lower lip. 



Some of the disputants even went so far as to 

 deny the existence of these glands and their accom- 

 panying orifices altogether; this would appear, how- 

 ever, to have been the result of faulty dissection . The 

 dispute was closed by a communication from Mr. It. 

 Beck, illustrated by a drawing, in which he showed 

 the orifice as being on the side of the fang near the 

 point. This communication may, I think, be fairly 

 said to have settled the question. 



The food which has been captured and killed 

 by the falces is next conveyed to the mouth. 

 This consists externally of an upper and under 

 lip, and a pair of maxillse or jaws. The upper 

 lip can only be detected externally by its hairy 

 tip, which is in reality merely the termination 

 of the palate. The lower lip and maxillse are both 

 also covered with hair; the latter are carneous in 

 their structure, and serve to masticate the food and 

 express the juices, which are then sucked up by the 

 lips. 



In a cavity above the palate is a transparent 

 glandular mass, which secretes a fluid considered to 

 be probably, functionally at least, the same as saliva. 



The mouth communicates by means of a short 

 oesophagus with the stomach. This viscus is of a 

 highly complicated and peculiar structure. It is 

 broad and flat, somewhat circular in form, and pos- 

 sesses on each side five branching cylindrical caeca?, 

 which extend up to the roots of the legs and palpi. 

 These csecse appear simply to serve the purpose of 

 exposing the food for an extended period to the 

 action of the gastric fluids. 



Erom the stomach the food 'passes into the ali- 

 mentary canal. This, at first narrow, expands at a 

 short distance from the stomach, again contracts, 

 and again expands at its extremity. 



The intestinal canal is enveloped on each side by 

 a dark granular mass of fatty tissue called the "fat- 

 body." This substance exists in a greater or less 

 degree in all the Arachnida pulmonaria; and when we 



