parent-forms

One other consideration is worth notice: with animals and plants that can propagate rapidly and are not highly locomotive, there is reason to suspect, as we have formerly seen, that their varieties are generally at first local; and that such local varieties do not spread widely and supplant their parent-forms until they have been modified and perfected in some considerable degree.

Golden Oldies: Transitional Fossils - The Panda's Thumb 2006

Independently of the question of fertility, in all other respects there is the closest general resemblance between hybrids and mongrels, —in their variability, in their power of absorbing each other by repeated crosses, and in their inheritance of characters from both parent-forms.

IX. Hybridism. Summary of Chapter 1909

The main cause, however, of innumerable intermediate links not now occurring everywhere throughout nature, depends on the very process of natural selection, through which new varieties continually take the places of and supplant their parent-forms.

X. On the Imperfection of the Geological Record. On the Absence of Intermediate Varieties at the Present Day 1909

Under free nature, we have no standard of comparison, by which to judge of the effects of long-continued use or disuse, for we know not the parent-forms; but many animals possess structures which can be best explained by the effects of disuse.

V. Laws of Variation. Effects of the Increased Use and Disuse of Parts, as Controlled by Natural Selection 1909

Lastly, looking not to any one time, but to all time, if my theory be true, numberless intermediate varieties, linking closely together all the species of the same group, must assuredly have existed; but the very process of natural selection constantly tends, as has been so often remarked, to exterminate the parent-forms and the intermediate links.

VI. Difficulties of the Theory. On the Absence or Rarity of Transitional Varieties 1909

With animals and plants that propagate rapidly and do not wander much, there is reason to suspect, as we have formerly seen, that their varieties are generally at first local; and that such local varieties do not spread widely and supplant their parent-forms until they have been modified and perfected in some considerable degree.

X. On the Imperfection of the Geological Record. On the Absence of Numerous Intermediate Varieties in Any Single Formation 1909

The existence of closely allied or representative species in any two areas, implies, on the theory of descent with modification, that the same parent-forms formerly inhabited both areas; and we almost invariably find that wherever many closely allied species inhabit two areas, some identical species are still common to both.

XV. Recapitulation and Conclusion 1909

Intermediate links have as a rule been wanting, and the seeds, which have often been sown, have not yielded reliable results, as no care was taken to preserve the blossoms from intercrossing with their parent-forms.

Species and Varieties, Their Origin by Mutation Hugo de Vries 1891

Thus the number of these will be very limited, and the primitive archigonian parent-forms can be nothing else than monads.

Freie wissenschaft und freie lehr. English Ernst Heinrich Philipp August Haeckel 1876

As we see the organic species, the multiform varieties of animals and plants, vary under our eyes through adaptation, while the similarity of their internal structure is reasonably explicable only by inheritance from common parent-forms, we are forced to assume common parent-forms for at least the great main divisions of the animal and vegetable kingdoms, and for the classes, orders, and so forth.

Freie wissenschaft und freie lehr. English Ernst Heinrich Philipp August Haeckel 1876