48 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



cylindrical gland, the only larger gland which dis- 

 charges here. On the inside of this horny cone 

 is attached a long yellowish cord or point, upon 

 which strong muscles are inserted in order to 

 move the cone against the spinneret. 



Mr. Underbill figures the spigots or large spin- 

 ning tubes which issue upon the posterior and 

 anterior spinnerets. 1 The former are situated upon 

 the interior margins and are connected with two 

 very large glands which are doubtless the cylin- 

 drical glands as heretofore described. Tliese spig- 

 ots are shown at Fig. 43 together with a portion 

 of the ducts leading to their appropriate glands 

 (not represented) which lie below the pyriform 

 glands. Fig. 44 shows one of these anterior spig- 

 ots, a.sp, compared with two spools ss. of the same 

 spinneret. Mr. Blackwall announced the 

 fact for the first time, so far as I know, 

 that the spools vary greatly in number 

 in different species, and also differ considerably in 

 si 2 * not onl y in individuals of the same species, 

 glandular epithelium is repre- but often even on the same spinnerets. The larger 



sented. cy.d, ducts belonging . /. ,- -r-, .. - , 



to the spigots; s P , probably of species of the Epeiroids have the spinnerets most 

 cylindrical glands, cy.g. amply provided with spools, and Blackwall ex- 



presses the opinion that the total number does not greatly exceed a thou- 

 sand, even in adult females of Epeira quadrata, whose weight is about 



SS -; 



FIG. 43. Anterior spinneret of 

 Epeira diademata. (After Un- 

 derbill.) ss, spinning spools ; 



Spools 

 Vary. 



Numbers 

 Vary. 



ss. 



twenty grains, and in many other 



species it is smaller. 



As illustrating the difference in 



various genera it may be stated that 

 Tegenaria domestica and 

 Tegenaria civilis, for ex- 

 ample, have less than four 



hundred spinning spools each. In 



Textrix agilis and Lycosa saccata 



the number is below three hundred. 



In Segestria senoculata it scarcely 



exceeds One hundred, and in many FIG 44 a spj spigot on anterior spinneret of Epeira dia- 

 Of the Smaller Spiders it is Still demata leading to cylindrical gland ; ss, spools of pyri- 



form glands, same spinneret. (After Underbill.) X 165. 



further reduced. 



The difference in the number and size of the spools connected with the 

 several parts of the spinnerets in the same species, and with similar pairs 

 in different species, is also very apparent. In spiders constituting the 



1 Science Gossip, 1874, page 181. 



