Extrachromosomal element delta in Drosophila melanogaster. VII. Relation to fertility in a second-chromosome line

The ID(b)-45 chromosome line usually carries an appreciable amount of delta b, but it is not susceptible to the killing action of this delta. The fertility of this line was examined when it carried various amounts of delta b. More than one third of the Cy/ID(b)-45 males and females tested became sterile when they carried cytoplasm of the Cy/Pm stock which is assumed to carry no delta b. The number of progeny is smaller when flies of this line are raised at 25 degrees C than at 28 degrees C at which temperature the multiplication of delta is accelerated. The progeny number was appreciably reduced when the flies were raised at 18 degrees C at which temperature the multiplication of delta is suppressed. This line could not be maintained at that temperature, since both males and females became sterile. Thus, the conclusion may be drawn that the presence of an appreciable amount of delta b is necessary for the gametogenesis of the Cy/ID(b)-45 flies.