258 ENTOMOLOGISK TIDSKRIFT I917. 



lower side of the antennse and therefore can be covered or 

 damaged without considerably hurting the animal. It is a 

 well-known fact that it is very difficult and frequently im- 

 possible to ascertain the function of sensory organs in Arthro- 

 poda, because we have only our own senses as starting-point, 

 and, excepting to a certain degree the eyes, the structure 

 of the external sensory organs in Arthropoda and in higher 

 \>rtebrata is extremely different. But I think to have shown 

 with tolerable certainty that the trichobothria in terrestrial 

 Arthropoda are scarcely auditory organs but tactile hairs of 

 special structure, perhaps also of somewhat special functions. 

 As partly mentioned above the trichobothria show, for the 

 rest, considerable differences as to the hair itself, which gener- 

 ally is long or extremely long, most frequently very thin but some- 

 times (Myriopoda) more robust, often glabrous but not infrequ- 

 ently with short or very short pubescence at least on its distal 

 part; the part of the hair inside the calicle is most frequently 

 cylindrical but sometimes (Myriopoda) much swollen; the 

 inner surface of the calicles differs considerably, being some- 

 times smooth, sometimes striated or sculptured, and on the 

 bottom of the calicle is frequently found a cup bearing the 

 hair, frequently no such thing. Further studies with high 

 magnifying power of sections of these and other of the 

 above-named sensory organs in different Arthropoda will 

 certainly reveal numerous fine modifications, and large num- 

 bers of experiments with living animals of various orders 

 will be needed before a deeper insight in the functions of 

 the trichobothria,, other kinds of sensory hairs, lyiiform or- 

 gans, etc., can be gained. 



V. List of main papers quoted. 



1885. Bertkau, Ph.: Ueber den Verdauungsapparat der Spinnen. 



(Archiv f. Mikrosk. Anatomie^ vol. 24, p. 398 — 451.) 

 1883. a. D.'ïHL, Fr.: Über die Hörhaare bei den Arachnoiden. 



(Zool. Anzeiger, vol. 6, p. 267 — 270.) 

 1885. h. Dahl, Fr.: Das Gehör- und Geruchsorgan der Spinnen 



(Archiv f. Mikrosk. Anatomie, vol. 24, p. i — 10.) 

 191 I. c. Dahl, Fr.: Die Hörhaare (Trichobothrien) und das 



System der Spinnentiere. (Zool. Anzeiger, vol. 37, p. 5 22 — 532.) 



