"Early stages in the development of Amphioxus. 1. Ovum with germinal vesicle; 2. four-cell stage; 3. external appearance of blastula; 4. blastula in section; 5. beginning of gastrula stage; 6. section of completed gastrula." -Thomson, 1916

Lancelet Stages

"Early stages in the development of Amphioxus. 1. Ovum with germinal vesicle; 2. four-cell stage; 3.…