This branch of science studies the developmental stages between
the zygote phase that results from the fertilization of a living
thing right through to birth. However, the concept of embryology
is mostly used to describe a branch of biology that studies the
development of animal embryos. Until the 18th century,
embryology was based more on speculation than on facts. The
reason was that genetics had not yet been discovered, and the
cell had not as yet been described. In general terms, the theory
at that time was that initially, all of an animal’s organs were
in a miniaturized state and only needed to open up and develop,
like the petals of a flower. Many naturalists maintained that
this initial state existed in the reproductive cells of a
woman’s, ovary. This theory, proposed long before by Aristotle,
maintained that the individual’s specialized structures
developed gradually from non-specialized ones previously in the
egg.137 But following the discovery under the microscope of
sperm, the male reproductive cel