REPORT OF COMMISSIONER OF FISH AND FISHERIES. 167 
Edible Mollusks. 
Mr. kh. G. Harrison and Mr. J. L. Kellogg, of Johns Hopkins Uni- 
versity, were employed at the Woods Holl laboratory during the sum- 
mer of 1890, under the direction of Prof. W. K. Brooks, to investigate 
certain natural-history problems relative to the oyster and other edible 
mollusks, and bearing upon their artificial cultivation. They worked 
conjointly on the embryology of the oyster, and made experiments re- 
specting the effects of density, temperature, sunshine, ete., on the oyster 
larva during its free-swimming and fixative stages. They also collected 
material for a study of the trematode parasites of the oyster and other 
bivalvés, Dr. Brooks having been led to believe that these organisms 
may have been instrumental in causing the deterioration of oyster beds 
in some cases. The general investigation of the anatomy, histology, 
and embryology of lamellibranchs was taken up by Mr. Kellogg and 
was conducted by him in accordance with modern methods of biological 
research. It is expected that these inquiries will furnish many impor- 
tant facts regarding the morphology of the common edible bivalves which 
will be of service to the fish-culturist. They will be continued during 
the summer of 1891. Dr. Wilson has also, during his investigations at 
Woods Holl, recorded many valuable observations respecting the breed- 
ing habits and organs of the long clam, quahog, mussel, and scallop. 
Sponges. 
Preliminary to a study of the life history of the Florida commer- 
cial sponges, which it is intended shall soon be taken up, Dr. H. V. 
Wilson began at Woods Holl, in the summer of 1890, an investi- 
gation of the breeding habits of certain species occurring in that vi- 
cinity. His observations were continued during the following winter 
and spring, most attention being paid to a silicious form which is com- 
mon on the wharf at the Fish Commission station. Dr. Wilson found 
that during the summer and early fall this species, instead of reproduc- 
ing by means of eggs, does so asexually through the formation of in- 
ternal buds or gemmules, solid oval bodies which swim about by means 
of cilia. Similar means of reproduction have been detected in the 
fresh-water sponges and in the genus Chalinula. The formation of 
these gemmules in the silicious species referred to, the character of the 
swimming larvee, and its metamorphosis into the adult sponge, were 
earefully studied by Dr. Wilson, who, judging also from observations 
made at the Bahama Islands, is led to believe that this method of 
propagation is common among marine sponges. Should this hold true 
with the commercial species, three possible methods of accomplishing 
their artificial cultivation would thereby be presented, namely, by 
means of the eggs, by means of the gemmules, and by cuttings. All 
the practical experiments made in this direction up to the present time 
have dealt only with the cuttings, and while that method may still 
prove to be the more satisfactory one, the others might present certain 
advantages in any attempt to improve the grade of sponges or to dis- 
tribute them over new grounds. 
