BTW, it kind of reminds me to the (mostly forgotten) lesson about organism's development.
After the initial cell splitting, the organism turns into a ball of cells (the Blastula). Then it will start to grow into something like this (the Gastrula ), with cells forming the outside (ectoderm) that became skin and nerves, and the flipped side became the inner wall (endoderm) that became digestive track and respiration.