preformationism

It was not until the late 19th century that preformationism was discarded in the face of cell theory.

A corollary of preformationism was a belief in the immutability of species.

Because of this assertion in particular, Harvey is often credited with being the father of ovist preformationism.

The concept has roots in preformationism as well as earlier folklore and alchemic traditions.

The groundbreaking scientific insights provided by Galileo and Descartes seemed instead to support preformationism.

In the history of biology, preformationism (or preformism) is the idea that organisms develop from miniature versions of themselves.

Epigenesis, then, in this context, is the denial of preformationism: the idea that, in some sense, the form of living things comes into existence.

Some animals' regeneration capabilities challenged preformationism, and Abraham Trembley's studies of the hydra convinced various authorities to reject their former views.

Malebranche also developed an original theory related to preformationism, postulating that each embryo probably contained even smaller embryos ad infinitum, like a Matryoshka doll.

Epigenesis is an old word that has more recently been used (see preformationism for historical background) to describe the differentiation of cells from their initial totipotent state in embryonic development.

When John Dalton's atomic theory of matter superseded Descartes' philosophy of infinite divisibility at the beginning of the 19th century, preformationism was struck a further blow.

The embryologist, Caspar Friedrich Wolff, famously refuted preformationism in 1759 in favor of epigenesis, though this did not sound the death knell of preformationist ideology.

This image, depicting what historian now refer to as the homunculus, has become iconic of the theory of preformationism, and appears in almost every textbook concerning the history of embryological science.

As opposed to "strict" preformationism, it is the notion that "each embryo or organism is gradually produced from an undifferentiated mass by a series of steps and stages during which new parts are added."

The historical ideas of preformationism and epigenesis, and the rivalry between them, are obviated by our contemporary understanding of the genetic code and its molecular basis together with developmental biology and epigenetics.

In fact, these inadequacies made for an atmosphere in which many lesser-known, and equally unconvincing, 19th century "arm-chair" hypotheses to be formulated and circulated in attempts to explain inheritance more adequately (see inheritance of acquired characters, maternal impression, telegony, preformationism, Geoffroyism, Pangenesis).