AGELENA N^VIA WALCKEN^R 163 



shape of a spiral tube, a conductor and various hard, chitinous 

 additional structures. The swelling of the haematodocha causes 

 the protrusion of the entire apparatus during copulation when 

 the embolus is introduced into the sperm receptacle of the 

 female. 



The four pairs of thoracic appendages are seven-jointed legs. 

 Two of them are directed forward and two backward, so that 

 the inner surface of the former corresponds to the outer surface 

 of the latter, and vice versa. The first joint which serves for 

 the attachment of the leg to the cephalothorax is called coxa or 

 coxopodite, the second trochanter or basopodite, the third femur 

 or meropodite, the fourth patella or carpopodite, the fifth tibia 

 or propodite, the sixth metatarsus or first dactylopodite, the 

 seventh tarsus or second dactylopodite. Some of the joints have 

 spines, the number and position of which furnish excellent sys- 

 tematic characters. At the end of the tarsus are two serrated 

 upper claws and a serrated median or lower claw. The first pair 

 of spinnerets called anterior or lower spinnerets are two-jointed 

 appendages of the fourth abdominal somite. It is probable 

 that they are homologous with the exopodite of a pleopod. 

 Their terminal joint is hemispherical and has comparatively 

 few spinning tubes. The appendages of the fifth abdominal 

 somite are the remaining four of the six spinnerets present in the 

 majority of spiders. They are biramous pleopods in which the 

 protopodite disappeared, the exopodite became the two-jointed 

 posterior or upper spinneret, while the endopodite is represented 

 by the much smaller, single-jointed median spinneret. The 

 terminal joint of the posterior spinnerets is long and thin, and 

 this joint as well as the median spinneret are the seat of numerous 

 spinning tubes. 



Integument. The integument consists of a chitinous 

 cuticle produced by the hypodermis. The latter is composed 

 of a single layer of epithelial cells. A supporting membrane is 

 produced by the hypodermis on its inner surface. The chitinous 

 cuticle forming the carapace, sternum and segments of the ap- 



