ZOOLOGY: L. R. GARY 
545 
and heterozygous females. In appearance and behavior, therefore 
these flies could not be distinguished from normal full-eyed males and 
heterozygous females. 
The possibility that the flies were due to contamination is not abso- 
lutely excluded, but the probabiHty is very low. In handHng food and 
flies the usual precautions were used. No larvae or flies appeared 
in the food. jars. Both vestigial-winged and long-winged races were 
handled, but no contamination of one with the other appeared. Three 
full-eyed males and one heterozygous female appeared in the vestigial 
race and all had vestigial wings; the others appeared in the long- winged 
race, and all had long wings. The fact that all females were heterozy- 
gous is a very strong argument against the probability of contamination. 
In case of contamination the females should, at least in the majority of 
cases, have been full-eyed; but no full-eyed females appeared. In the 
face of this evidence it is almost necessary to conclude that these flies 
appeared by reverse mutation and not by contamination. 
The appearance of such reverse mutations can not readily be explained 
on the basis of the presence and absence theory nor on the theory of 
association and disjunction, but it is not difficult to explain on the theory 
of chemical change. If a chemical change in the constitution of some 
substance, probably in the chromosomes, produced the bar-eyed mutant^ 
then a reversion of that chemical change would produce the original 
substance and so bring about the reappearance of the original character, 
the full eye. 
The data upon which this report is based together with a more de- 
tailed discussion will be pubHshed in the near future in the report on the 
selection experiments. 
THE PART PLAYED BY ALCYONARIA IN THE FORMATION OF 
SOME PACIFIC CORAL REEFS 
By Lewis R. Cary 
DEPARTMENT OF BIOLOGY. PRINCETON UNIVERSITY 
Communicated by A. G. Mayer, June 22, 1917 
Following up my studies on the coral reefs of the Tortugas Islands, 
in which it was found that in this particular region the alcyonaria con- 
tribute more limestone to the reefs in a given time than do the stony 
corals, a simflar study of the coral reefs was undertaken, under the 
auspices of the Carnegie Institution of Washington, at the Island of 
Tutuila, American Samoa. 
