236 THE HARMONIES OF NATURE. 



is so extremely minute as to require a high magnifying power 

 for its perception, communicates with a fine or narrow excretory 

 canal (c) situated in the interior of the mandible, and given off 

 from the true secreting organ a gland (d) lodged in the inter- 

 space of the muscles of the thorax, or breast, whose compression 

 causes the immediate propulsion of the liquid. 



A still more wonderful apparatus is that which serves the 

 spiders for the formation of their threads. The spinnarets, or 

 organs which emit the glutinous fluid, are generally six in num- 

 ber, and situated at the posterior part of 

 the body. Each of the spinnarets is pierced 

 by an infinite number of small holes, or 

 beset with hairy appendages terminating in 

 fine-drawn points, from each of which there 

 escape as many little drops of a liquid, which 

 becoming dry the moment it is in contact 

 spmnareis with the air, forms so many delicate threads. 

 Immediately after the filaments have passed 

 out of the pores of the spinnaret, they unite first together and 

 then with those of the neighbouring spinnarets to form a com- 

 mon thread; so that the thread of the spider, which measures 

 only l-4000th or even l-8000th of an inch in diameter, is com- 

 posed of an immense number of minute filaments, perhaps 

 several thousand, of such extreme tenuity that the eye cannot 

 detect them until they are all twisted together into the 

 working thread* 



But why this complicated process, it may be asked ; why this 

 original excessive subdivision of a filament, which, when com- 

 plete, far surpasses in fineness the finest thread which can pos- 

 sibly be spun by machinery proceeding from human hands ? 

 The reason is obvious, for it was absolutely necessary that as 

 soon as the glutinous fluid emerged from the body, it should 

 instantly consolidate into a thread firm enough to be worked or 

 not to give way too suddenly under the spider's weight ; and it 

 is evident that by its extreme division, so beautifully provided 

 for by the microscopical perforation of the sievelike spinnarets, 

 the process of desiccation, having a larger surface to act upon, 

 must be considerably hastened. Thus there is nothing super- 

 fluous in this wonderful mechanism, which, perfect in design 



