ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 577 



luminosity to it ; if kept for much more than an hour in water, the eggs 

 begin to lose their photogenic properties ; but if withdrawn at such a 

 moment, the light-giving power gradually returns. It is easy to show, as 

 by pricking the egg with a teasing needle, that the substance contained 

 in the shell of the egg is luminous by itself; if parts of the tissue of the 

 luminous organ are rubbed lightly on a sheet of paper there are luminous 

 marks, but nothing of the kind occurs if the shell remains intact. 



The photogenic power is exercised in the egg without the aid of tracheae, 

 nerves, or special anatomical elements, and the continuity of the light is 

 the result of the vital processes of the egg of Lampyris noctiluca. 



Senses of Insects.* — M. A. Forel contributes a most interesting and 

 exhaustive account of experiments made by himself and many others on the 

 much discussed problem of the senses of insects. 



(1) In regard to sigJit of ants, he notes especially these three conclu- 

 sions : — (a) They perceive light, and particularly ultra-violet (Lubbock) ; 

 (6) they really see the ultra-violet rays, without eyes they are almost indif- 

 ferent to them, and only respond to solar light more or less intense ; (c) the 

 dermatoptric sensations are feebler among ants than in the animals which 

 Graber studied. 



(2) After reviewing new and old experiments, as to the sense of smell in 

 insects, he notes the following general facts : — (a) In many insects which 

 are essentially directed by sight, as in the Libellulids and Cicadas, the 

 antennse are rudimentary, and the sense of smell likewise. During the 

 night these insects are passive, while during the day they trust to their 

 power of sight, or possibly in some cigalids also to hearing ; (&) the sensitive 

 region, in spite of Graber's protestations, is situated in the antennae, espe- 

 cially in those parts where the antennary nerve ramifies ; (c) in certain 

 insects, as in most Diptera, the antennae probably serve almost solely for 

 smelling purposes ; (<^) in other cases, however, where they are mobile, as 

 in the Hymenoptera, they are used for detecting their food or their mates 

 at great distances. 



(3) As distinct organs of taste, M. Forel regards the nervous terminations 

 (a) on the proboscis of flies (Leydig), (h) on the jaws and on the base 

 of the tongue (Meinert), (c) on the end of the tongue (Forel), and (d) on 

 the palate or on the epipharynx (Wolff). 



(4 and 5) Forel's results as to hearing are as yet too negative to admit of 

 notice. He finally discusses the sense of touch in its various manifestations, 

 and the last chapter of his interesting memoir discusses the relation of the 

 five senses to the general psychical life of insects. 



Cell of the Honey Bee.j — Prof. H. Hennessy has a second note on the 

 geometrical construction of the cell of the honey bee; he finds that a 

 sphere may be inscribed within the cell from a point measured from the 

 vertex at a distance equal to the side of one of the lozenges, and with a 

 radius equal to half the long diagonal of this lozenge, while another sphere 

 with a diameter equal to three times the size of the lozenge circumscribes 

 the triangular pyramid at the summit. If D' be the diameter of the 

 inscribed sphere, and D that of the exterior sphere, the relation between 

 them may be expressed thus : — 



D' \2/ 



* Rec. Zool. Suisse, iv. (1887) pp. 161-240. 

 t Proo. Roy. Soc. Lond,, xlii. (1887) pp. 17ti-7. 



