No. 2.] THE ADHESIVE ORGAN OF AMIA. ' 483 
columnar cells (Fig. F). The central ends of these cells 
next the cavity of the cup are distended, apparently with 
mucus. The peripheral third of each cell stains heavily on 
account of the larger amount of yolk it contains. The nucleus 
also lies in the peripheral portion of the cell. The walls of the 
cups are continuous at their edges with the adjacent ectoblast, 
so that the cups have the appearance of being thickenings of 
the ectoblast. Fig. F, which shows a film-like layer of ecto- 
blast closing the mouth of the cup, belongs to a slightly earlier 
stage, but represents fairly the structure at the hatching stage. 
~-- W. VS. 
Fic. F—Section through one of the vesicles of the adhesive organ of an 
embryo of Amia a little younger than that shown in Plate, Fig. 4. 
c. vs., cavity of the vesicles; w. vs., wall of the vesicle. Other let- 
ters as in preceding figures. The inner layer of ectoblast has dis- 
appeared over the cavity of the vesicle, but the outer layer still 
remains, 
During the interval between the fourth and hatching stages 
important and rapid changes are thus seen to have taken 
place in the adhesive organ: First—Each fundament has been 
divided into as many vesicles as there were dilatations of 
its lumen in stage four. This division has resulted apparently 
from an extension and deepening of the grooves, present in 
stage four on the posterior faces of the diverticula, but the 
precise method of this process is unknown. The result is that 
each of the dilatations of stage four becomes the cavity of 
