460 



THE INVERTEBRATA 



the number of tracheae is much reduced, even to a single pair from 

 each stigma. The variations in the development of the tracheae are 

 recorded in the opening section on the Arachnida (p. 447). 



'7 



i Fig- 339- 



Fig. 338. 

 Fig, 338. Pedipalp of Tegenaria guyonii, the large house spider. From 

 Shipley and MacBride. i, coxa; 2, gnathobase, the so-called maxilla; 

 3, trochanter; 4, femur; 5, patella; 6, tibia; 7, tarsus; 8, palpal organ. 



Fig. 339. Front view of head of Textrix denticulata. From Warburton. 

 I, head; 2, eyes; 3, basal joint of chelicerae; 4, claw of chelicerae. 



1.. 



Fig. 340. Diagrammatic view of expanded palpal organ. From Shipley and 

 MacBride. i, tarsus; 2, bulb; 3, vesicula seminalis, and 4, the opening of 

 its duct which is protected by 5, the conductor ; 6, haematodocha which is dis- 

 tended with blood when the palpal organ is expanded; 7, alveolus ; 8, tarsus. 



The spinning glands are shown in the diagram in the ventral part 

 of the abdomen. In a web spinner like Epeira, there are five types of 

 glands of diverse structure and function, all opening by minute pores 

 on the spinnerets. Thus the ampulliform glands supply the radial lines 

 of the webs, and the spiral lines are made by the aggregate glands 



