SPINNING APPARATUS OP GEOMETEIO SPIDERS. 65 



performed by glands apparently so distinct. Apstein attempts 

 its solution by reasoning wbicli is mainly indirect and, in my 

 opinion, misleading. It occurred to me that the problem might 

 be attacked in a more direct manner, and with this view the 

 experiments to be now described were performed. 



A spider of this group usually trails a line from its spin- 

 nerets while walking. With a little dexterity it can be quickly 

 seized, and imprisoned in such a manner that the spinnerets 

 from which the line is proceeding can be microscopically 

 examined. 



This may be best eflFected by means of a piece of wood about 

 the size and shape of a microscope slide, with a narrow band of 

 cloth attached by its end to one extremity. The cloth band 

 is then held in front of the crawling animal, which may, with 

 a little practice, be thus trapped between the cloth and the 

 wood, so that the band passes beneath the cephalothorax, 

 leaving the abdomen free for examination with the lately 

 emitted line still attached. 



The fourth pair of legs must be kept from interfering with 

 the experiment by pins suitably adjusted. The spinnerets will 

 now be in their quiescent position, and the precise origin of the 

 threads therefore invisible. If, however, it be gently drawn 

 forwards, i.e. towards the animal's head, certain facts with 

 regard to it become at once clear. As, however, the phe- 

 nomena differ at different times, we must take the various cases 

 in succession. 



In the simplest case (fig. 9) one of the anterior spinnerets will 

 be pulled forward with the thread, which will be easily seen to 

 consist of a single line emanating from one large tube. 



More frequently (fig. 10) the line will be double issuing 

 from similarly situated tubes on the inner sides of the two an- 

 terior spinnerets. This is probably the most usual case, and I 

 have drawn out from a spider many yards of such a double line 

 of silk, its origin being all the time plainly visible. 



It is important to note that there is no adherence between 

 the two lines, which remain perfectly distinct throughout their 

 whole parallel course. 



