ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 235 



rings are the last to disappear, and gradually the whole becomes 

 dark. Here and there, however, several bright points remain long in 

 activity. 



If the separated abdomen of a healthy insect be excited by slight 

 pressure a flash of light can likewise be observed. It is, however, 

 less intense and the process is slower. The bright rings persist for 

 a considerable time round the dark spots, and they often appear 

 irregular and interrui)ted. In the already darkened portion numerous 

 luminous points are seen, which sometimes join together and form 

 new rings, which again break up and vanish. 



The difficulty of both these modes of observation, owing to the 

 movement of the living insect in the one case, and of the mechanical 

 excitation in the other, led Prof. Emery to poisoning the insect 

 with vapoiir of osmic acid. In such cases he was able to observe 

 round the dark spots of the portion in full light smaller, fainter, 

 sometimes unconspicuous spots, arranged with a certain regularity. 



Comparing these observations with preparations stained with 

 carmine, or hardened with alcohol and clarified with caustic potash, 

 it was seen (1) that the large round spots represented the central 

 portion of the " digitiform acini " of T. Tozzetti, or the " Tracheen- 

 endzellen " of M. Schultze ; (2) that the luminous portion represented 

 parenchymatous cells, and the smaller dark spots the nuclei of the 

 latter. 



The bright portions, i. e. the parenchymatous cells, are observed 

 to become discontinuous and to fade gradually, sometimes leaving 

 bright persistent points. The contours of the cells and the nucleus 

 within are sometimes distinctly visible. Prof. Emery gives figures of 

 the various phenomena. He is thus able to affirm with certainty that 

 the light of the Luciola originates in the parenchymatous cells, and 

 withdraws his previously expressed opinion that the luminosity 

 originated mainly in the cells of the cylindrical lobes formed from 

 the matrix of the tracheae. In full luminosity the dazzled eye cannot 

 detect any diffijrences of intensity ; the uniformity is perhaps due to 

 reflection, or it may be that the cells of the deeper layer have also 

 to a less degree the power of luminosity. During medium luminosity, 

 at any rate, the combustion is exclusively confined to the parenchy- 

 matous cells of the transparent superficial layer of the organ. 



Researches on the Meloidse.* — M. H. Beauregard communicates 

 the first part of a detailed study of the Meloidas. 



In discussing (a) the integument, he maintains the probability that 

 its softness is for the most part due to the small quantity of salts in 

 proportion to organic matter, as is suggested by the results of 

 analyses. The varied and often brilliant colours are due either 

 (1) to the phenomena of interference, or (2) the presence of special 

 pigments, or (3) to the effect of coloured or uncoloured hairs. 

 (1) The brilliant green of the common Cantharid, which has been 

 sometimes referred to the presence of a green oil due to the chloro- 

 phyll of the leaves eaten by the insects, is, however, visible in young 



♦ Journ. Auat. et Physiol. (Robin), xxi. (1885) pp. 483-534 (2 pl«.). 



