"... mechanisms to explain the adhesion of the second layer of cell.

Three possible explanations suggest themselves:

1. that haemocytes recognize and respond to differences in each other; the "dorsal" surface of a primary adherent cell appears different because there has been redistribution of particular surface epitopes, charged molecules, etc. Random contact by another haemocyte would lead to recognition, adhesion, and slightly less modification of the secondary cell's surface, and so on;

2. that adherent primary cells secrete adhesive materials so that other randomly contacting haemocytes either become physically trapped or adhere via specific or non-specific adhesions; or

3. that primary cells release "recruiting factors" that stimulate changes in adhesion (and locomotory behaviour) of the secondary cells."

LACKIE (1988)