Assertion : Evolution for Darwin was gradual while deVries believed mutation caused speciation and hence called it saltation (single step large mutation).

Reason: Embryological support for evolution was  proposed by Ernst Heckel.

Both assertion and reason are true but reason is not the correct explanation of assertion.

The correct answer is Option (2)- Both assertion and reason are true but reason is not the correct explanation of assertion.

In the first decade of twentieth century, Hugo deVries based on his work on evening primrose brought forth the idea of mutations – large difference arising suddenly in a population. He believed that it is mutation which causes evolution and not the minor variations (heritable) that Darwin talked about. Mutations are random and directionless while Darwinian variations are small and directional. Evolution for Darwin was gradual while deVries believed mutation caused speciation and hence called it saltation (single step large mutation).

Embryological support for evolution was also proposed by Ernst Heckel based upon the observation of certain features during embryonic stage common to all vertebrates that are absent in adult. For example, the embryos of all vertebrates including human develop a row of vestigial gill slit just behind the head but it is a functional organ only in fish and not found in any other adult vertebrates. However, this proposal was disapproved on careful study performed by Karl Ernst von Baer. He noted that embryos never pass through the adult stages of other animals.