ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 59 



refuse to fly, an observation in accordance with the familiar fact that 

 during the passage of a thick cloud, or similar darkening, insects 

 usually cease to fly. M. Plateau's observations were made on insects 

 provided with or without ocelli in addition to the compound eyes, and 

 with the same results. 



From numerous experiments on Diptera, Hymenoptera, Lepido- 

 ptera, Odonati, and Coleoptera, of which tabular summaries are given, 

 M. Plateau concludes that insects with compound eyes, with or 

 without ocelli, pay no heed to differences of form in the light- 

 openings of a half-darkened room, but fly with equal readiness to 

 the apparently easy and apparently difiScult way of escape, that they 

 are attracted to the more intensely lightened opening, or to one with 

 apparently greater surface, and that in short they cannot by vision 

 distinguish form, or only to a very slight extent. 



Sense of Smell in Insects, &c.* — In continuation of his well- 

 known researches on light-perception, in which the general sensitive- 

 ness of the body-surface was demonstrated in many animals, Prof. 

 Veit Graber has made an extensive series of experiments on the 

 degree and localization of the sense of smell. Among his interesting 

 results the following are the most important : — 



(1) Odours are perceived by many invertebrates (Molluscs, Dis- 

 cophora, Chaetopods, Insects, &c.) with extreme rapidity — sometimes 

 in one-third of a second, and even through an intervening layer of 

 1-2 mm. of water ; (2) that the sensitiveness is enormously quicker 

 than was exhibited by the vertebrates experimented on (amphibians, 

 lizards, birds) ; (3) that insects deprived of their feelers are still able 

 to smell, in various degrees in different insects and with different 

 odours, some fine odours being apparently perceptible only through 

 the feelers ; (4) that the perception of smell by way of the respira- 

 tory organs, which has been often maintained, is not at any rate 

 rapid or important ; (5) that in some cases the palps are more sensitive 

 than the feelers, and that therefore the latter cannot, any more than 

 the eyes in his previous researches, be described as in any way 

 possessing a monopoly of sensitiveness. 



Foot-glands of Insects.j — In reference to Herr J. Dahl's re- 

 searches on the foot-glands of insects,^ Herr H. Dewitz asserts that 

 these are for the most part only a corroboration of his work on the 

 same subject.§ Apart from the question of priority, he affirms, with 

 an appeal to Dr. K. Brandt and Dr. Joh. Frenzel, that the structures 

 on the soles of Locustidae are not mere rods, but are hollow, and that 

 similarly the tarsal attaching hairs of other insects have a terminal 

 opening, situated either at the very end or somewhat laterally. 



* Biol. Centralbl., v. (188.5) pp. 385-98. 



t Arch. f. Mikr. Anat., xxvi. (1885) pp. 125-8. 



X See this Journal, v. (1885) p. 989. 



§ SB. Gesellsch. Nat. Freuude Berlin, 1882, Jan. and July; Zool. Anzelg., 

 vii. (1884) pp. 400-5 ; Arch. f. Naturg., 1. (1884) pp. 146-93 ; Pfluger'a Arch. f. d, 

 Gesammt. Physi.-l., xxxiii. (1884) pp. 440-81. See this Journal, iv. (1884) 

 p. 716. 



