Whatever the evolutionary model we adopt, in the case of sexual reproduction, the process has an embryological significance because this is the way to generate individuals and to perpetuate the life. The connection between evolution and embryology is a necessary event. In this evolutionary context, the key question is: how two species are formed from the same biological unit? During the first half of the 20th century embryologists as Richard Goldschmidt, Conrad Waddington, and Walter Garstang answered the question from a heterodox point of view. They introduced new concepts that changed the way to thinking the evolution. This essay analyzes this unorthodox thought and its scientific impact.