114 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



hairs, and the linear thickenings of the tegument, in approaching these 

 points, surround them in concentric circles. I have heretofore suggested 

 that all action of the muscles upon the abdominal tegument may have 

 much influence in the distribution of color for the formation of various 

 patterns which mark spiders.^ 



Fig. 77 represents the tarsus and metatarsus of a ■L5'cosid foot (Taren- 

 tula), taken from the rejected skin. The tendons by which the tarsus and 

 claw are moved are shown within the leg, and one sees the 

 „ p , thickening of the tendons (e.t) at their free ends upon which 

 the muscles are inserted. The claw and the entire dentition 

 thereof, as may be seen, have left a perfect cast in the moulted tegument. 

 The tendon passes from the claw in the form of a thick 

 double cord, traversing the tarsus apart and uniting at the 

 articulation with the metatarsus, which joint is traversed 

 nearly to the articulation with the tibia, where the cords 

 join with the short stout muscles in- 

 serted into the cuticle at that ®-^. 

 „, , point. The silk glands in 

 moulting undergo changes 

 both in form and number, as 'with the 

 tubuliform glands of tarentula shown 

 at Fig. 78, after the second and third 

 moults. Three different forms of glands 

 appear (gl 1, gl 2, gl 3), corresponding 

 possibly with tlie ampuUate, tubuli- 

 form, and pyriform glands of Epeira. 



Adult spiders of the two sexes, according to Wagner, do 

 not always possess the same silk glands. The females have 



Fig. 77. Moult of 

 final joints of a Ly- 

 cosid foot, show- 



FiG. 78. Silk glands of a ta- 

 rentula at the periods of 

 second and third moults. 



ing the tendons 



(e.t) that move the glauds uot observcd in the males, which this author be- 



tarsus and claw, ligyes scrvc to Supply the cocooniug silk. However, in the 



earliest stages of life the silk glands of the male and female are alike. 



XL 



These physiological facts in the moulting processes of spiders Mr. 

 Wagner has himself thus summarized : 1. Tlie rejection of the old skin 

 constitutes only a part of the moulting process, and that a sec- 

 ondary one. 2. The processes of a moult, in some of their features, 

 commence a comparatively long time before, and end after the 

 rejection of the skin and in connection therewith. 3. The spider, partly 

 before casting off the old skin, partly at the momeivl of the act, and even 

 for a brief period afterward, is deprived of some of its faculties : of sight, 



Sum- 

 mary. 



' Proceed. Acad. Nat. Sci., Philadelphia, 1888, page 173. 



