Who pronounced the basic principles of embryonic development?

The correct choice is von Baer, who is known for formulating the basic principles of embryonic development in the early 19th century. His work, particularly on the development of mammalian embryos, led to the formulation of what is now known as von Baer's laws. These laws emphasize that during the early stages of embryonic development, embryos of different species exhibit similarities that reflect their common ancestry before diverging into species-specific stages. This idea contributed significantly to the understanding of developmental biology and the concept of evolutionary relationships among organisms.

Understanding von Baer's contributions allows for a deeper appreciation of how embryology can provide insights into evolutionary biology, highlighting the interconnectedness of life. His observations laid a foundation for future research in developmental biology, making his principles instrumental in the study of how organisms develop from a single fertilized egg into complex structures.