— Plate 26. — 



Fig. I. — Diagram of a sagittal section of entrance of the trap of Utricu- 

 lar ia gibba, with terminology. 

 Fig. 2. — Entrance of U. gibba, exoleta etc. in sagittal section. The 

 arrows (3, 4) indicate the general direction of the movements of prey 

 in approach. The structure of the pavement is seen through the door 

 as if transparent. 



Fig. 3. — U. gibba. View of threshold and door edge, as seen from the 

 viewpoint indicated by the arrow i in fig. 2. Arrow i indicates the 

 direction of thrust of the side of the door on the lateral reaches of 

 the threshold; arrow 2, thrust of the door lateral hinges on the middle 

 piece, and of this against the pavement in its middle reach. 



Fig. 4. — Sagittal section of entrance of U. longifolia. 



Fig. 5. — U. purpurea. The knob at the middle of the door. See fig. 

 2-4, PLATE 27. 



Fig. 6. — U. vulgaris. 



Fig. 7. — The same, the door swung widely open. 



Fig. 8. — Diagram of the sagittal section of the door of U. purpurea to 

 show that movement of the knob up or down lifts the door edge; c, 

 center of rotation; d, b, displacements of point a when the trigger 

 hairs are touched downwardly or upwardly, respectively. 



Fig. 9. — Quadrifid hair of U. gibba, quite young. 



Fig. 10. — Reflexed quadrifid hair of U. neottioides. 



Fig. II. — Quadrifid hair of Poly pom pholyx. 



Fig. 12. — The same, side view. 



Fig. 13. — The same, diagram of the shape of a single one of the four cells 

 of the capital. 



