Gastrulation in Amphibians:

Bottle Cell Function - Context-Dependent

Bottle cells undergo apical constriction, but their normal function depends on performing this constriction at the border of the vegetal yolk mass, which is apparently relatively non-deformable. To see this, bottle cells can be cut out of the normal location and allowed to constrict in vitro. Instead of making a line, they produce a pit (micrograph adapted from Hardin and Keller, 1988).

Alternatively, bottle cells can be freed from their usual surroundings by making lateral cuts; in this case they pull together into a condensed mass (micrograph courtesy of Dr. Ray Keller, Univ. of Virginia).