SPINNING APPARATUS OP GEOMETRIC SPIDERS. 69 



existence as threads implies a degree of dryness inconsistent 

 with complete fusion. 



As far as I have been able to trace these lines they have 

 appeared to emanate from the intermediate spinnerets. They 

 are much more elastic, however, than the radial lines, and can 

 therefore hardly proceed from the Ampullaceal orifices. 



The only other paired orifices on the intermediate spinnerets 

 are those of the Tubuliform glands. Now, an important 

 function of these glands is undoubtedly, as Apstein remarks, 

 the spinning of the egg cocoon, for they are always distended 

 with yellow fluid in the female just before the deposition of 

 ova, and comparatively inconspicuous after, while the cocoon 

 consists of yellow silk. 



If, however, they also furnish the ground-threads, this would 

 help to explain their presence in the male spider, which has not 

 hitherto been very easy to understand. 



The objections to this view are, first, that cocoon silk is not 

 especially elastic, and secondly, that I have not been able to 

 find threads in the cocoon of the precise diameter of the ground- 

 threads. 



In spiders of the species under consideration the following 

 thread-diameters were found to be fairly uniform : 



Cocoon line '006 mm. 



Anterior Ampullaceal . 

 Ground-line of spiral . 

 Intermediate Ampullaceal 



•003 



■0025 



•0016 



The imperfect view I obtained of the origin of the ground- 

 thread led me to think that though it proceeded from the inter- 

 mediate organs, it had some subsequent relation to the posterior 

 spinnerets. 



It is possible, therefore, that Apstein is correct in supposing 

 that the Aggregate glands, which debouch on the inner side 

 of the posterior spinnerets, deposit the viscid matter above 

 described. 



The arguments hitherto adduced in support of this view are, 

 first, the convenient arrangement of the Aggregate orifices for 

 such a purpose, and secondly^ the presence of these glands in 



