The laws of heredity : their definite meaning and interpretation / editor: Henry Smith Williams, M.D., LL.D.

Date:
[1914]
Catalogue details

Licence: Public Domain Mark

Credit: The laws of heredity : their definite meaning and interpretation / editor: Henry Smith Williams, M.D., LL.D. Source: Wellcome Collection.

    18/32 page 16
    we have thus far purposely ignored — the familiar fact, namely, that each higher organism is not the offshoot of a single parent but a product of the union of two parents. Be it plant or animal, every individual above the very lowest strata of organic life owes its be- ing to the union of two germ cells. It represents the commingling of two strains of racial germ- plasm. Pollen grain unites with ovule in the case of the plant; sperm-cell with ovule in the case of the higher animal; and each type of cell conveys its own coterie of hereditary potentialities. This is the essential and primary fact that complicates the entire situation. The fact of double parentage is one that will be seen at a glance to remove all simplicity from the formula “like produces like.” For no two individuals are precisely alike; no two cells of the germ-plasm carry precisely the same ancestral traits. The briefest consideration will suggest some at least of the complications that necessarily re- sult when more or less divergent germ-plasms are commingled. Of course, if two ancestral germ-plasms are too widely divergent they cannot commingle at all. The two organisms are then said to be mutually infertile. This was formerly supposed to be the case with most different species. Indeed the test [16]
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