Blastula (Gk. blastos, “sprout,” + dim. ending –ulasource)

Looked up for personal edification while reading Dawkins’ The Greatest Show on Earth (extremely highly recommended).  The preceding stage in the development of an embryo is called the morula, from the Latin morus, “mulberry.”  So the little mulberry becomes a little sprout, and later (third week?) a little stomach (gastrula).  (“How to Get a Flat Belly” Google ad accompanies one gastrula definition.  You may want a small stomach, but not that small.)