No. 2.— The Gastrulation of Aurelia flavidula, Per. & Les. 
By Frank Smiru.} 
Precepine the appearance of Goette’s (87) publication in 1887 upon 
the development of Aurelia aurita and Cotylorhiza tuberculata, the gas- 
trulation of Aurelia had been regarded, in the light of the studies of 
Kowalewsky, Haeckel, Claus, and others, as the result of invagination or 
at least of a process nearer to invagination than to any other method of 
gastrulation. 
Gvette’s work seemed to show, however, that, instead of an invagina- 
tion, there is an ingression of cells to form the entoderm, and that the 
first result of this ingression is the production of a solid gastrula, or 
sterrogastrula, which is only subsequently hollowed out, and is put into 
communication with the exterior through the formation of a prostoma 
at a still later period. Recently, in a paper dealing especially with the 
development of Cotylorhiza tuberculata, Claus (°90) reaffirms the posi- 
tion taken in his previous paper (’83), in which the gastrulation in 
Aurelia was represented as being simply a modification of invagination. 
In recent papers by Hamann (’90) and McMurrich (’91), Goette’s views 
are adopted, and form part of the basis for statements that, in the devel- 
opment of the Scyphomeduse, invagination, instead of being the rule, is 
the exception. 
This want of agreement among those who have given the subject 
most attention makes the determination of the actual method of gastru- 
lation in Aurelia a matter of considerable interest, and it may be 
assumed that any contribution to the solution of the question will not 
be unwelcome, 
Early in the current year, at the suggestion of Dr. E. L. Mark, I 
undertook to investigate the method of gastrulation in A. flavidula. 
Through the kindness of Mr. B. H. Van Vleck of the Boston Society 
of Natural History, I was enabled to spend two months of the summer 
of 1887 at his seaside Laboratory at Annisquam, Mass., where I then 
collected the material used in the present study. The embryos were 
killed with picro-nitric acid, and preserved in 90 per cent alcohol, in 
which they have been kept during the three intervening years. Of the 
1 Contributions from the Zoölogical Laboratory of the Museum of Comparative 
Zoölogy, under the direction of E. L. Mark, No. XXIX. 
VOL. XXII, — NO, 2, 
