The basic principles of embryonic development were pronounced by 
(A) Von Baer
(B) Weismann
(C) Haeckel
(D) Morgan

Hint: The basic principles of embryonic development were pronounced by the scientist who was born on 17 February 1792. He explored European Russia and Scandinavia. He was a member of the Russian Academy of Sciences, a co- founder of the Russian Geographical Society.

Complete step by step answer:
The basic principles of embryonic development were pronounced by Von Baer and he was the first president of the Russian Entomological Society, making him a distinguished Baltic German scientist. He was a naturalist, biologist, geologist, meteorologist, geographer, and a founding father of embryology.

Additional Information:
Four laws given by Von Baer are :
- First law states that general characteristics of the group to which an embryo belongs develop before special characteristics.
- Second law states that General structural relations are likewise formed before the foremost specific appearance.
- Third law states that the form of any given embryo doesn't converge upon other definite forms, but separates itself from them.
- Fourth law states that the embryo of a higher animal form never resembles the adult of another animal form, like one less evolved, but only its embryo.
Von Baer through his laws described the development (ontogeny) of animal embryos while also critiquing popular theories of animal development at the time. His laws of embryology provided a framework to research the relationships and patterns between the development of varied classes of organisms, and thus the patterns between ontogeny and therefore the diversification of species on Earth (phylogeny). Von Baer's laws, published in 1828.
Von Baer's first two laws explained how the animal embryos develop and whether or not they progress from preformed structures.
Von Baer's third and fourth laws tell us that as the ontogeny of an animal embryo progresses, the embryo's different stages of development represent lower animals' adult forms.
So, the correct answer is ‘(A) Von Baer’.

Note: In 1828, while performing at the University of Königsberg in Königsberg, Germany, Karl Ernst von Baer proposed four laws of animal development, which came to be called von Baer's laws of embryology.Not only in the field of embryology, but Karl Ernst von Baer had also pursued a variety of other areas of study which includes medicine, botany, zoology, and anthropology.