SPINNING APPARATUS OP GEOMETRIC SPIDER3. 71 



Summary. 



1. Facts newly established. — A spider's line does not 

 consist of many strands fused or woven together, but ordinarily 

 of two or four distinct threads. 



The framework and the radii of circular snares are supplied 

 by the AmpuUaceal glands. 



The Acinate and Piriform glands are those mainly em- 

 ployed in binding up captured prey. 



The " trailing line " consists primarily of AmpuUaceal 

 threads, sometimes strengthened by contributions from the 

 Acinate and Piriform glands. 



The ground-line of the spiral is double only, and the two 

 strands are bound together merely by the viscid matter which 

 envelops them. 



2. Corroborative of Apstein. — The "attachment discs" 

 are furnished by the Piriform glands. 



The Tubuliform glands supply the silk for the egg-cocoou. 



The viscid matter of the spiral is probably the product of the 

 Aggregate glands. 



Finally, the origin of the spiral ground-line is uncertain, 

 but it may proceed from the Tubuliform orifices on the inter- 

 mediate spinnerets. 



