146 THE MICROSCOPE. Oct. 



which are beset with polished conical points resembling 

 teeth. 



To the upper end of this furrowed case is fixed by a 

 hinge-joint the fang, which is a curved claw-like organ, 

 formed of hard chitine, and consisting of two parts,-a 

 swollen oval base, which is highly polished, and a more 

 slender tip, the surface of which has a silky lustre, from 

 being covered with very fine and close set longitudinal 

 grooves. This whole organ falls into the furrow of the 

 basal joint, when not in use, exactly as the blade of a clasp- 

 knife shuts into the haft ; but when the animal is excited 

 the fang becomes stiffly erected. 



By examining the tip of the fang we see that it is not 

 brought to a fine point, but that it has the appearance of 

 having been cut off slantwise just at the tip; and that it 

 is tubular, both the fang and the thick basal joint are 

 permeated by a slender membranous tube, which is the 

 poison duct. This connects with a lengthened oval sac 

 where the venom is secreted. 



When the spider attacks a fly, it plunges into its vic- 

 tim the two fangs. These act downward, not from right 

 to left as do the jaws of insects. At the same time a 

 very small drop of pojson is secreted in each gland, 

 which, oozing through the duct escapes from the perfor- 

 ated end of the fang into the wound, and rapidly pro- 

 duces death. The fangs are then clasped downward, 

 carrying the prey, which they powerfully press against 

 the toothed edges of the stout basal piece. By tliis 

 means the nutritive fluids of the prey are pressed out 

 and taken into the mouth, when the dried and empty skin 

 is rejected. This poison is of an acid nature, as litmus- 

 paper, when pierced by an irritated spider, is turned red 

 as far around the perforations as the liquid spreads. 



A Post Graduate course of bacteriolog-y has been estab- 

 lished at the Sidney University, N. S. W. 



