ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 597 



tho loss of energy is very slight, whereas in artificial light it may be 

 as much as 98 per cent. 



The author analyses the causes of the admirable economic superi- 

 ority, and ascribes it to the following causes : — 



1. There are a number of chemical rays in this light as may be 

 shown by photography, but there is only a small proportion of them ; 

 the result must be ascribed to the existence of a fluorescent substance 

 which has been discovered in tho blood of Pyrophorus, and which, by 

 penetrating into the organ, gives it the special and brilliant character 

 which distinguishes the light. The greater number of the chemical 

 rays are transformed into very brilliant fluorescent rays of a medium 

 wave-length. 



2. Optic analysis shows that the light is in great part composed 

 of rays similar to those which are found at those points of the 

 spectrum where experience has fixed the maximum of illuminating 

 intensity. 



3. There is no loss by heat-radiation ; the amount of heat given 

 -off, even at the time of greatest activity, is infinitesimal. 



4. There is no reason for supposing that there is any conversion 

 of energy into electricity. 



5. This marvellous light is physiological because it is of vital 

 origin, and because no other source is as well adapted to the wants of 

 the organ of vision in the animal series. 



Honey-dew.* — M. Boudier finds the composition of honey-dew 

 from the Aphis of the laburnum to be as follows : — Cane-sugar 57 • 25 ; 

 inverting sugar 16*25; dextrin, mucilaginous substances, albumi- 

 noids, &c, 26*5 per cent. It frequently contained llucedincs©, which 

 possibly, in their development, have transformed a portion of the cane- 

 sugar into inverting sugar. In damp weather there are developed 

 on the leaves covered with honey-dew large numbers of fungi belong- 

 ing to the genus Cladosporium. 



j8. Myriopoda. 



Early Development of lulus terrestris.j — Mr. F. G. Heathcote 

 experienced considerable difficulty in preparing the ova of lulus 

 terrestris, owing to the hard chitinous chorion and the great amount 

 of food-yolk. Attempts to remove the chorion by Bobretski's method 

 were failures ; Perenyi's fluid burst the chorion quickly, but the 

 contents escaped ; in the result Mr. Heathcote cut sections of the 

 ova with the chorion still on. The sections were most satisfactorily 

 stained by Grenacher's alum-carmine. 



The ovum, when within the ovary, is surrounded by a follicular 

 envelope, has a large nucleus and a single large nucleolus, which 

 stains very deeply. Sections made from ova late on the day of oviposi- 



* Assoc. Fran, pour l'Avancement ties Sci., Congres de Blois, 1884, 8 pp. 

 See Bull. Soc. Bot. France, xxxii. (1885) Rev. Bibl., pp. 122-3. 



t Quart. Journ. Micr. Sci., xxvi. (1880) pp. 449-69 (2 pis.). Troc. Roy. Soc. 

 Loud., xl. (1886) pp. 73-6. 



