Production of Local Depressions in the Development of Drosophila Pupæ

Abstract

IN a previous paper¹, which is now in the press, I have shown that the respiration of the pupæ of Drosophila melanogaster is depressed by carbon monoxide, and that the effect is, to a certain extent, reversible by light. (This latter fact may be inter preted as a dissociation, under the influence of light, of the chemical compound, which carbon monoxide forms with the iron-containing respiratory enzyme.) These findings make it possible to apply Runnström's device², which he used to obtain local inhibition of the cleavage process in Ciona eggs. The apparatus, constructed by Prof. J. Runnström, consists of a microscope with a strong condenser, through which a narrow beam of intense light can be focused on the stage of the microscope. If a living object is put under the microscope in a carbon monoxide atmosphere (for example, in a Carrel dish, filled with the suitable gas mixture), and part of it is illuminated with the beam, while the rest is kept shielded from light, its respiration should be more intense in the regions illuminated, than in the regions in the dark. Thus the apparatus is to a certain extent the reverse of the so-called ultra-violet point radiation, by which local defects can be produced with a narrow beam of ultra-violet light.