3S6 PHYSIOLOGY OF THE INVERTEBRATA. 



turbances occurring in the antennal integuments, which are 

 solid and often provided with hairs and bristles. Among 

 those Insecta in which these organs are very long, filiform, and 

 movable in various directions, they serve, like the vibrissa of 

 many Mammalia, to announce the presence of external bodies. 

 With very many other Insecta, they are very movable, and 

 are distinctly used as tactile organs, like the fingers of the 

 human hand. It is also by means of these organs that insects 

 perceive the various conditions of the atmosphere, especially 

 the temperature, and thereby regulate their movements and 

 actions. With those Insecta, where the parts of the mouth are 

 modified into organs of suction, it is quite evident that the 

 extremity of the proboscis is the seat of a very delicate sense 

 of touch. Also with those female insects having an ovipositor, 

 which is used to deposit their eggs in holes of various depth, 

 the apex of this organ must be endowed with the same 

 power."* 



The extremities of the limbs in many Insecta are also tactile 

 organs. Besides these special devices, the skin of the Insecta 

 is sensitive to touch. In spite of the chitinous covering, these 

 animals feel strongly the contact of external objects at any 

 point of their own bodies. This is due to the sensitiveness of 

 the underlying membrane. 



The sense of taste is confined to the mouth and pharynx. 

 This sense is, as a general rule, connected with the tactile 

 sensation of the buccal cavity, and also with the olfactory 

 sensation. 



In the Insecta, as well as in other Arthropoda, a specific 

 sensory epithelium is present at the entrance to the buccal 

 cavity : this is stated to possess a gustatory function. 



In the Insecta the cuticular appendages of the antennae, in 

 which the ganglionated extremities of nerves occur, are con- 

 sidered to be olfactory fibres. Dr. G. Hauserf has recently 

 examined the olfactory organs of the Insecta. In all the 



* Siebold's Anatomy of the Invertebrata (American edition), p. 414. 

 •f Zeitschrift fur Wissenschaftliche Zoologie, vol. 34, p. 367. 



