50 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



were unilnnuly eight, two of whicli were situated on the inferior surfuce 

 of tlie spinneret at a greater distance from the extremity tliau tlie rest, 

 and were minute and ahnost contiguous. 



It is a fact deserving notice that tlie spiuuing spools are not always 

 developed simultaneously on these spiimerets, six, seven, and eight being 

 sometimes observed on one, while five, six, or seven are to be seen on the 

 other. This remark is applicable not to the anterior spinnerets alone, but 

 to tiic intermediate ones also, which, in mature individuals, are further 

 niodilicd by having the extremities of the terminal joints directed forwards 

 at ri<'ht amdes to their bases. The same condition was observed in a 

 species of Drassus and in Segestria senoculata. It is not improbable, tliere- 



foi"e, that other species, and j)er- 

 haps all spiders, follow the same 

 law of development. 



This whole system of liquid 



silk supply is regulated by th(> 



compression of surround- 



sp-- 



Muscular 

 System. 



ing muscles, which act 

 upon the several glands 

 ill the manner of the hand when 

 squeezing upon the rubber l)ulb of 

 a spraying tube. The contents are 

 forced out of the glands in this 

 liquid condition, tlirougb the long, 

 delicate ducts, into the hollow si)in- 



Ki(^ 40. Epeira diademata. sp (p), spigot of treeform nillg tubcS, whcUCe they isSUC ill 

 gland on posterior spinneret ;ssipl, spools of pyriform • . ■ . fhrOUB-h the exterior 

 glands on same. (After Underbill.) ■: 165. miUUlL jeiS llllOUgll llie CXltllOl 



oi)eiiings or mouths of the spools. 

 As the points of the spools or tips of the spinnerets are approximated, a 

 number of tliese jets flow together, and hardening instantly upon contact 

 with the air, form the thread or line familiarly known as the spider's web. 



The excretory ducts, as well as the silk glands themselves, are encircled by 

 a filirous or muscular coat, which loo.sely surrounds them, and seems to be a 

 continuation of the outer coat or sac itself. The spinnerets are connected 

 with, or surinount the integument of the abdomen, by means of diverging 

 bands of niviscular fibres, which eiialde them to move in different directions. 

 These muscles are })laced immediately beneath the skin, and their expanded 

 extremities are inserted into it so that they are separated with it, unless 

 dissected very carefully, i 



All the spinnerets are thus pruviili'd witii many muscles which cause 

 the approachment of all the spools of one S2)inneret against one another, 

 as also the convergence of all the six spinnerets towards a central point, 

 in order to produce in this way a single thread. For this purpose the 



' Meade. 



