XII
HYPERMORPHOSIS

IF those characters which only appear in the adult stage of the ancestor are retarded so that they do not appear in the descendant by the time development ceases, they will become vestigial, as shown in the previous chapter. But if the time when development stops is relatively delayed, it will be possible for the descendant to add characters on to the adult ancestral stage. Referring again to the example of intersexuality in moths, male characters do not normally appear by the time development ceases; but if the time of maturity is postponed, these male characters can and do make their appearance. This additional development, or hypermorphosis, may then be expected in cases where the evolution has resulted in progressive increase in size, or where the time of maturity is delayed relatively to the body- characters. The cases to be considered here conform to the principle of 'overstepping' of Müller, of 'prolongation' as suggested by Franz, and partly to the principle of 'anaboly' as enunciated by Sewertzow.

The best example of hypermorphosis is that of the Pteraspida of the Lower Devonian described by E. I. White. In Poraspis the dorsal shield of the adult is characterized by the pattern of the lateral-line canals which extend over the whole of it. In the later species, Pteraspis leathensis, P. rostrata, and Rhinopteraspis dunensis, the dorsal shield is formed of the same size as in Poraspis, but to its edges is added a peripheral extension which increases in size in the successive species. The adult form of the ancestor is therefore repeated in the descendants and is 'overstepped' by the addition of new structures and an increase in size. But the adult ancestral form is not pressed back into earlier stages of development in the descendants, and there has therefore been no abbreviation or recapitulation. The whole ancestral ontogeny has been repeated in full, and full-size.

Other examples are given by J. S. Huxley ( 1932). The limbs of lambs of domestic breeds pass through stages in which their proportions correspond to those of adult wild (and therefore presumably ancestral) sheep. Schultz's demonstration of the

-100-

Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items
Notes
Cite this page

Cited page

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Note: primary sources have slightly different requirements for citation. Please see these guidelines for more information.

Cited page

Bookmark this page
Embryos and Ancestors
Table of contents

Table of contents

  • Title Page iii
  • Preface v
  • Contents vii
  • List of Illustrations xi
  • I- Stages of Development And Stages of Evolution 1
  • II- Ontogeny 14
  • III- The Speeds of the Processes Of Development 22
  • IV- Phylogeny 29
  • V- Heterochrony 34
  • VI- Caenogenesis 40
  • Conclusion 51
  • VII- Deviation 52
  • Conclusion 61
  • VIII- Neoteny 63
  • Conclusion 90
  • IX- Vestigial Structures Due To Reduction 92
  • X- Adult Variation 97
  • XI- Vestigial Structures Due To Retardation 99
  • XII- Hypermorphosis 100
  • XIII- Acceleration 104
  • Conclusion 110
  • XIV- Paedomorphosis And Gerontomorphosis 111
  • XV- Repetition 125
  • XVI- Embryology and Taxonomy 134
  • XVII- Embryology and Homology 146
  • XVIII- The Germ Layers 154
  • Conclusions 168
  • XIX- Conclusions 170
  • Bibliography 175
  • Index 191
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen
Items saved from this book
  • Bookmarks
  • Highlights & Notes
  • Citations
/ 202

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Search by... Author
    Show... All Results Primary Sources Peer-reviewed

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.