Aggregate cultures are primary cell cultures prepared from dissociated fetal cells. In rotation-mediated culture under rigorously controlled conditions, the isolated cells are able to reaggregate spontaneously, and to form a large number of practically identical spheres but in your case it dispersed in the form irrugular spherical shape due poor dispersant

This type of aggregation could be a signal of celular death ?

I'd like to clarify that the flask is an Erlenmeyer but looks spherical due an optical effect