1879.]} 325 [Brooks 
General Meeting. November 19, 1879. 
Vice-President Mr. 8. H. Scudder, in the chair. Forty- 
six persons present. 
The following candidates were elected to Associate 
Membership: Messrs. Walter P. Manton, E. Bentley 
Young and Prof: John M. Ordway of Boston; Mr. Quincy E. 
Dickerman of Somerville; Prof. C. H. Fernald, Orono, Me.; 
Prof. Geo. H. Stone, Kent’s Hill, Me.; and Mr. Warren 
Upham, of Nashua, N. H. 
Mr. Ernest Ingersoll gave a sketch of the present and past 
distribution of the Oyster in the Gulf of Maine and adjacent 
coasts. 
Prof. A. Hyatt read a paper by Mr. A. P. Whitfield on 
some remarkable changes undergone by Lymnaea megasoma 
in confinement. 
The following paper was presented by title : 
THE DEVELOPMENT OF THE DIGESTIVE TRAcT IN MOLLUSCS. 
By W. K. Brooks, Pu.D., AssocraTE IN B1oLoGy, JoHNns Hop- 
KInS UNIVERSITY, BALTIMORE, Mp. 
As long as the homology of the germ-layers and of the structures 
derived from them in the subordinate groups of Metazoa remains in 
uncertainty, any general hypothesis as to their homology throughout 
the entire group of Metazoa is clearly premature ; and I do not 
think that any one who is acquainted with the recent literature on 
the development of Mollusca will dispute the statement that our 
knowledge of the mode of origin of the endoderm, the digestive 
cavity, the mouth and the anus in the various groups of the Molluscs 
is at present too fragmentary and inconsistent to admit of any general 
comparisons. 
While certain observers state that there is a real invaginate gas- 
trula stage of development, others deny that there is any thing of the 
kind in the embryology of any mollusc; and of those who describe a 
more or less modified gastrula stage some state that the blastopore 
