Prior to gastrulation, the chick embryo consists primarily of a quasi-two-dimensional disc of about 50,000 cells. The first visible morphogenetic process of gastrulation is extension of the primitive streak. The streak, which is formed from a narrow multilayer cohort of cells originating from the posterior marginal zone, establishes the future vertebrate axis of the organism. Early gastrulation in humans is based on the same fundamental process of primitive streak extension. Recent live-cell imaging studies of chick gastrulation in the Weijer lab have shown that just prior to (and during) streak extension, cells in the disc undergo collective movement, tracing out two large counter-rotating vortices. The mechanisms underlying extension of the streak and the vortex motion are presently unknown, although experimental evidence points to either cell intercalation or chemotaxis as plausible candidates. In this talk I will present three disparate theoretical ideas, originating from physical analogs of vortex formation, concerning these mechanisms, along with instantiations of these ideas using grid-free computer simulations of streak formation.