A hybrid drum rudiment is when two rudiments are combined into one rudiment. The ectodermal wall of the tube forms the rudiment of the nervous system. It is a rudiment of the extensor muscle of the caudal vertebrae of other animals. After this the larva develops an echinus or juvenile rudiment, which will become the juvenile. The Berger Lesson 25 is a Hybrid Rudiment named for Fritz Berger. The first written rudiment was drawn up in Basel, Switzerland in 1610. The term "rudiment" in this context means not only "basic", but also "fundamental".