GENETICS: H. J. MULLER 
619 
^ It would be interesting to know whether corals and calcareous algae deposit as much 
CaCOs in the dark as in the light. Corals from deep water are smaller, more fragile, and 
deposit less CaCOs than those of shallow water, but the same is true of animals without 
symbiotic algae. The deposition is, however, related to the pH, since Palitzsch has shown 
that the pH decreases with depth. 
^ Amer. J. Sci., New Haven, 41, 1916, (473). 
AN OENOTHERA-LIKE CASE IN DROSOPHILA 
By Hermann J. Muller 
THE RICE INSTITUTE. HOUSTON 
Communicated by T. H. Morgan, September 14, 1 91 7 
Although the large bulk of the Drosophila work has been remarkably 
self -consistent, and amenable to orderly and definite rules of factor trans- 
mission, yet from the outset the ideal scheme has been confronted with 
' two unconformable cases. These are the cases of beaded wings and of 
truncate wings, both of which seemed to belie the idea of clear cut 
segregating gens. In the case of beaded wings, which will be briefly 
reported here,^ many generations of selection were carried out by Mor- 
gan with the purpose of obtaining a pure breeding stock, yet for several 
years it was impossible to attain this object. The character showed all 
the pecuHarities which would be expected as a result of factor fluctua- 
tion and miscibility. It was increased in intensity as a result of selection 
yet its essential variabihty remained, and the latter was proved by 
crosses to be genetic, for Morgan found that reversed selection produced 
a m.arked and immediate retrogression in the proportion of beadeds 
thrown. Finally, however, he did obtain a race which threw no nor- 
mals, but the reason for this change in behavior seemed now just as 
difficult to discover as the cause of the previous variability. On crossing, 
various apparently irregular results and aberrant ratios followed. 
The work of Dexter, which showed that environmental conditions and 
factors in both the second and third chromosomes are all concerned in 
the development of this character, provided valuable information for the 
present investigation. Starting from Dexter's finding that there was a 
chief factor for beaded in chromosome IIP an attempt was made by the 
writer to find the precise location of this gen. It proved to lie at the 
extreme right hand end of the known factors in the third chromosome, 
being two and a half units beyond the factor for rough eyes, which is 
otherwise the furthest factor to the right. It was found also that the 
apparently pure beaded stock is not homozygous for beaded, but in 
reality contains two very different kinds of third chromosomes. It was 
by investigating this phenomenon, with the aid of the data secured in 
