Morphological design and Theory of Preformation: Theory of Preformation

Morphological design and Theory of Preformation: Theory of Preformation

Theory of Preformation

Theory of Pre-formation was popular in the 18th century (now unfortunately totally discredited). According to the theory, an individual develops by simple enlargement of a tiny fully formed organism (a homunculus) that already exists in the germ cell. All that would have to happen was for the male’s seed to unite with the female’s egg to start the development of this miniature person. For a long period of time many prominent people subscribed to this theory and some went as far as to figure out how many preformed humans were carried by Eve (200 million). They claimed that after all of these preformed people were developed, our race would end .

It had its origins in one of Swammerdam’s most notorious experiments in which he dissected a silk-worm caterpillar and correctly showed the presence of adult structures such as wings, legs and antennae within its body, prior to pupation (this is true of all moths and butterflies).

In the late nineteenth century two men, Wilhelm Roux (1850-1924) and Hans Driesch (1867-1941) formulated their own theories of embryonic development. Roux’s experiments were designed to prove that a modified theory of preformation was correct. In his Mosaic Theory of embryonic development he claimed that if there is a preformed pattern within the fertilized egg, then one cell remaining alive would form only one part of an embryo. Roux went on to kill one cell and only developed half embryos out of the remaining cells.

Meanwhile, Driesch set out to disprove the Mosaic Theory of preformation and put forth his own theory of preformation. His experiments were done on sea urchins, unlike Roux he did not kill any cells, he merely removed one cell and developed it. Both of the remaining cells developed into complete sea urchins, as a matter of fact in sea urchins it has been discovered that this is possible even up to where the zygote contains four cells. If further experiments take place after the four cell development stage, just as in Roux�s results, you�d get incomplete embryos. Driesch was fortunate in his selection of experimental animals because such cell division is limited to just a few species

Modern scientists have found both men to be partially correct with their theories�correct in that the embryo is �preformed�, however, it is argued that this occurs in the form of the inherited genetic code of deoxyribonucleric acid (DNA). Research has proven that the �blueprint� for development is contained in the DNA.