On the Law of Development commonly known as von Baer’s Law ; and on the Significance of Ancestral Rudiments in Embryonic Development

Abstract

The generalisation commonly referred to as v. Baer’s law is usually stated as follows :—Embryos of different members of the same group are more alike than the adults, and the resemblances are greater the younger the embryos examined. It appears to be pretty clear that v. Baer held some such view as this,1 and there can be no doubt that it is a view which is largely taught at the present day.2 In fact, I think it is safe to say that all zoologists are brought up with this view as one of the fundamental postulates of their science.