294 IXSECT ARCHITECTURE. 



of inconceivable fineness. In the following figure, this 

 wonderful apparatus is represented as it appears in the 

 microscope. 



We do not recollect that naturalists have ventured to 

 assigii any cause for this very remarkable multiplicity of 



'I 



Spinnerets of a Spider magnified to show the Spinnerules. 



the spinnerules of spiders, so different from the simple 

 sjDinneret of cater j)illars. To us it appears to be an admir- 

 able provision for their mode of life. Caterpillars neither 

 require such strong materials, nor that their thread should 

 dry as quickly. It is well known in our manufactures, 

 particularly in rope-spinning, that in cords of equal thick- 

 ness, those which are composed of many smaller ones united 

 are greatly stronger than those which are spun at once. In 

 the instance of the spider's thread, this principle must hold 

 still more strikingly, inasmuch as it is composed of fluid 

 materials that require to be dried rapidly, and this drying 

 must be greatly facilitated by exposing so many to the air 

 separately before their union, which is eftected at the 

 distance of about a tenth of an inch from the spinnerets. 

 In the following figure each of the threads represented is 

 reckoned to contain one hundred minute threads, the whole 

 forming only one of the spider's common threads. 



Leeuwenhoeck, in one of his extraordinary microscopical 

 observations on a young spider not bigger than a grain of 

 sand, upon enumerating the threadlets in one of its threads. 



