n. (Biol.) Formation and separation of laminæ or layers; one of the methods by which the various blastodermic layers of the ovum are differentiated. [ 1913 Webster ]

☞ This process consists of a concentric splitting of the cells of the blastosphere into an outer layer (epiblast) and an inner layer (hypoblast). By the perforation of the resultant two-walled vesicle, a gastrula results similar to that formed by the process of invagination. [ 1913 Webster ]

pos>n. (Chem.) A nitrogenous strongly basic chemical substance (C3H6N6), structurally 2, 4, 6-triamino-1, 3, 5-triazine, produced from several cyanogen compounds, and obtained as a white crystalline substance; -- formerly supposed to be produced by the decomposition of melam. Called also cyanuramide. It is used as one of the starting components (together with formaldehyde) in the preparation of melamine resins, including the commercially marketed Formica (TM). It is solid at room temperature, and sublimes at temperatures approaching 250° C, decomposing at 345° C. Density 1.573. HCP61 [ 1913 Webster + PJC ]

n. A thermosetting plastic formed by the reaction of melamine and formaldehyde. It is used for molding and for preparing laminated sheets used to surface counter tops, walls, and furniture. The commercially marketed Formica (TM) is one type of melamine resin. [ PJC ]