We present measurements and simulation of fluid flow and sphere motion in a pressure-driven microfluidic sorter designed for Drosophila embryos. We simulate the flow fields for different channel layouts and study the effect of control pressure, chamber length and entrance length on switching time to find geometries and conditions for optimized embryo movement. We validate the sorter design with fluid experiments in devices fabricated from silicon and Pyrex wafers. The experimental and simulated results are compared both qualitatively and quantitatively by examining the concentration distribution of fluids. This type of microfluidic sorter is promising for micromanipulation of a variety of biological cells, and provides automated operations for higher throughput and accuracy.