Russian zoologist who discovered and introduced the concept of different embryonic tissue layers. He received his training in embryology while living in Germany. Embryology is the study of how individual cells develop from a fertilized egg into a new organism. In 1817 Pander began his observations on the embryos of chicken eggs. This study helped him discover embryonic tissue layers, which he called the primordial or germ layers. Today we know these layers as the ectoderm, mesoderm, and endoderm. It is interesting to note that Pander began this study because he was one of the few people who could afford to purchase the eggs and pay an attendant to watch the incubators.