Facts in the Physiology of Spiders and Insects. — Blackwell. 47 



propel the fluid to the open extremity of the delicate hair-like papillas, 

 exactly as the non-viscid fluid, propelled by the couti'action of the muscles 

 connected with the vessel that secretes it, passes out of, but is not 

 ejected in a stream from, the minute orifice situated near the extrem- 

 ity of the fang that teimi nates the folces. 



To this extent I am prepared to admit the influence of the muscles 

 that contribute directly or indirectly to the action of the spinning 

 apparatus ; but that a remarkable viscid fluid, which immediately 

 becomes concrete on exposure to the air when drawn out in a filament 

 of such marvelous tenuity as the lines produced by spiders, can, not- 

 withstanding its extreme levity and flexibility, and quite ii-respective 

 of the size of the animals producing it, be propelled by any physical 

 power with ^rhich they are endowed in a straight line of many feet ht 

 length, through a resisting medium liable to rapid fluctuations like the 

 atmosphere, does appear to be in the higliest degree impi'obable, and 

 is, as already asserted, directly at variance with the result of an exten- 

 sive and elaborate experimental investigation of the subject, a brief 

 abstract of which 1 proceed to give. 



Spiders, if placed on wooden or metallic rods set upright in glass 

 vessels with perpendicular sides, containing a suflicient quantity of 

 clean water completely to immerse their bases, in vain attempt to effect 

 an escape from them in a still atmosphere; all their efl'orts to accom- 

 plish their desired object, though perseveringly persisted in, proving 

 quite unavailing when they are placed under a glass shade, or in any 

 situation where the air is not liable to be disturbed. However, should 

 individuals thus insulated be exposed to a current of air, either natur- 

 ally or artificially produced, they instantly turn the abdomen in the 

 direction of the breeze, and emit from the spinners a little of their 

 viscid secretion, which, being carried out in a line by the current, be- 

 comes connected with some object in the vicinity, and aftbrds them the 

 means of regaining their liberty. This line uniformly moves in the 

 direction and with the velocity of the stream of air ; but if, while pro- 

 ceeding from the spinners, it be subjected to the action of a lateral or 

 opposing current, it immediately becomes deflected from its course by 

 the new. impulse thus imparted to it. 



I may here remark that numerous species belonging to various^ 

 genera of spiders, — -Drassus ater, Clniflo similis, Ergatis latens, Tegena- 

 ria civilis, Cuelotes saxatilis, Dysdera crythrina, and Oonops pulcher, for 

 example, — though provided with highly organized spinners, yet do not 

 appear to be endowed with the instinct to avail themselves of a current 

 of air for the purpose of transmitting their lines to a distance. 



The manner in which the lines of spiders are drawn out from the 



