THE srixxixa ukgans. 



41 



Fifi. 33. Pyriform silk glands. 



in diameter (about one-twelfth of an inch), lyiiift" close to the bases of the 

 spinnerets. (Fig 30, py.g.) Tn form the individual glands are long, oval, 

 pear shaped vessels, 0.22 mm. long, or, expressed approximately in linear 

 measure, say one hundred and fifteen of average length wouW make an 

 inch. In Argiope I iiiid the average length about one eighty-fifth of an 

 inch. At the inferior end they diminish grad- 

 ually, passing into a duct which narrows towards 

 the point of discharge, and which, together with 

 a compact bundle of similar ducts, enters the 

 interior of the spinneret, each one to discharge 

 through its appropriate separate spinning tube. 

 The wall of the gland contains a single cell stra- 

 tum of a diameter of from 0.020 mm. to 0.024 

 mm. Tliese cells contain a quantity of small 

 drops, which consist of a strong refractory sub- 

 stance that agrees in appearance with the spin- 

 ning material within the ducts. This glandular 

 wall incloses a large middle cavity, which is entirely tilled with a viscous 

 liquid spinning substance. The duct which projects from this 

 Psrriform ^i,^^^^ possesses at the beginning a diameter of 0.024 mm. ; nar- 

 rows very soon after exit from the gland to the diameter of 

 0.01 to 0.012 mm. That is to say, the termination of the duct is about 



one twenty-five-hundredth of 

 an inch in diameter. At this 

 width it runs unaltered to its 

 place of exit from the spin- 

 ning tube. 



These pyriform glands, as 

 preserved in Argiope cophina- 

 ria, while agreeing in 

 GlTudf'^ general form vary a 

 good deal in details, 

 as shown by comparing the 

 tigures, 31, 32, and 33. Some 

 of them are vermiform in 

 shape, Fig. 33, v ; some are 



Fig. 34. View of the cyliudrical glands, cy.g, and treeform , • ,i ■£ 



glands, tr.g, of Epeira diademata. py.g, cluster of pyriform Stnctly pyritorm, p ; SOmC aTC 



glands, d, bundle of ducts leading therefrom, spn, a spin- ('Qril'lte FisT 32 C * aild SOlllC 

 neret into which the glands lead. (After Meckel.) ' ' ' _^. 



have long caudal i)arts, lig. 

 31, pe, whicli in general appearance resembl(> the cylindrical glands, but 

 are on a much smaller scale. Tlie v(>rmif()rni glands contain a yellowish 

 white substance. The otlier glands contain a somewhat similar material, 

 but of a deeper yellowish color, and broken into distinct globules; while 

 others contain a brownish liquid which has already been alluded to. This 



