both refer to movie chains (i.e., Loews, AMC Theatres) with movie theatres that screen more than one film at a time, as opposed to single-screen theatres. A multiplex has from 2 up to 16 screens, a megaplex has 16 or more screens; plex is the abbreviation for a multiplex theatre.
A morula (Latin, morus: mulberry) is an early stage embryo consisting of cells (called blastomeres) in a solid ball contained within the zona pellucida.
Eight-cell embryo (approximately 72 hours after insemination). The morula, a collection of around 30 cells (blastomere), is created at about 96 hours. Because these cells arise only through the cleavage of the zygote and all are found inside the pellucid zone, which cannot expand, no growth is seen. Every new cell is thus only half as large as the cell from which it derives.