SPINNING APPARATUS OF GEOMETRIC SPIDERS. 33 



The spider will probably tire of having its silk thus drawn 

 out — a process which it can only influence indirectly. Were 

 its hind legs free it would seize the thread and break it. It 

 sometimes contrives to do this by a rapid movement of its spin- 

 nerets, but occasionally it decides to strengthen the thread 

 instead. The spinnerets are accordingly actively rubbed to- 

 gether^ and a little flocculent mass of silk appears upon the 

 line^ which is thereafter seen to consist of four strands, two of 

 finer calibre having made their appearance between the former 

 lines (fig. 11). To see their origin the anterior spinnerets must 

 be kept forward by a gentle strain on the thread, and the pos- 

 terior spinnerets thrust aside with a needle. The new lines 

 may then be traced to the intermediate spinnerets, and proceed 

 from large spinning tubes on the inner side. Again, the four 

 lines remain distinct and non-adherent. 



Should the spider still resolve on strengthening the line a 

 further rubbing together of the spinnerets occurs, and presently 

 a large number of strands are seen to proceed from the nume- 

 rous hair-like tubes on the anterior spinnerets (fig. 12). The 

 four previous lines are still distinguishable by their greater 

 thickness. 



If after drawing out several inches of this compound line it 

 be slightly slacked, a puff of air separates the strands, showing 

 that, though contiguous, they are not adherent. 



Lastly, upon rare occasions, the whole battery of tubes seems 

 to be brought into play, the posterior spinnerets contributing 

 their quota to the strengthening of the line. Thus the " trail- 

 ing line," as I have called it, will be found at any moment 

 to be constituted as indicated in one of the cases above 

 described. 



It appears, therefore, that such a line usually consists of 

 either two or four non-adherent threads emanating from what 

 Apstein has shown to be the origin of the Ampullaceal 

 glands, and that it may on occasion be strenghened by con- 

 tributions from the Piriform and Acinate glands opening 

 upon the anterior and posterior spinnerets respectively. 



It was next attempted to apply the same direct method to 



VOL. XXXI, PART I. NEW SER. C 



