Development in the presence of antibodies specific for Group 2 sigN proteins. AX4 cells were placed on nitrocellulose filters to induce multicellular development. Filters were placed over pads soaked on phosphate buffer alone (PDF) or containing preimmune serum (preimmune) or a serum raised against a Group 2-specific peptide (Anti-P2). At 15 hours of development, the antiserum filter was divided in two parts. One half was placed on a new pad soaked in PDF alone (PDF) and the other on a pad soaked in PDF containing Group 2 antiserum (Anti-P2), as shown in the lower part of the right-hand panels. Pictures were taken at the times of development indicated at the left of the panels with a stereomicroscope (Bar, 0,15 mm).