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Hyatt, Alpheus in correspondent 
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From:
Charles Robert Darwin
To:
Alpheus Hyatt
Date:
13 Feb 1877
Source of text:
Maryland Historical Society (Alpheus Hyatt Papers MS 1007)
Summary:

Regrets that F. Hilgendorf proved so greatly in error ["Planorbis Multiformis", Monatsber. K. Akad. Wiss. Berlin (1866): 474–504; "Noch einmal Planorbis Multiformis", Z. Dtsch. Geol. Ges. 29 (1877): 50–62].

Discusses polymorphic species.

Surprised that shell form developed from various different progenitors.

Reminds CD of C. Nägeli’s conclusions on Hieracium.

But still retains belief expressed in first edition of Origin that variation in protean species is neither advantageous nor disadvantageous.

Contributor:
Darwin Correspondence Project
From:
Charles Robert Darwin
To:
Alpheus Hyatt
Date:
8 May 1881
Source of text:
Maryland Historical Society (Alpheus Hyatt Papers MS 1007)
Summary:

Aware that AH thinks CD has done nothing to advance the good cause of the descent theory.

Obliged for gift of AH’s [Tertiary species of Planorbis at Steinheim (1880)].

Contributor:
Darwin Correspondence Project
From:
Charles Robert Darwin
To:
Alpheus Hyatt
Date:
14 Dec [1872]
Source of text:
Maryland Historical Society (Alpheus Hyatt Papers MS 1007)
Summary:

Sends copy of last edition of Origin.

Respecting AH’s theory that acceleration of growth produces new characters, urges AH to examine decapods that do and do not pass through zoea stage. Believes there are no marked differences between them.

Contributor:
Darwin Correspondence Project
From:
Charles Robert Darwin
To:
Alpheus Hyatt
Date:
21 Jan [1875]
Source of text:
Maryland Historical Society (Alpheus Hyatt Papers MS 1007)
Summary:

Thanks for note and extract.

Will be glad to read AH’s memoir when published [? "The Jurassic and Cretaceous Ammonites collected in South America by Prof. James Orton" Boston Soc. Nat. Hist. [Proc Mem Jnl!?] 17 (1875): 365–72].

Recalls AH’s visit to Down.

Contributor:
Darwin Correspondence Project
From:
Charles Robert Darwin
To:
Alpheus Hyatt
Date:
4 Dec [1872]
Source of text:
Maryland Historical Society (Alpheus Hyatt Papers MS 1007)
Summary:

If decapod does not pass through zoea stage, is this acceleration? If hypothetical adult retained zoea characters, would this be retardation? Believes obliteration of growth stages frequently due to natural selection. Most interesting points in AH’s letter deal with senile characters. CD attributes them to laws of growth not selection. Explains degraded characters as result of readaptation to simpler conditions. Believes no innate tendency to progressive development exists.

Hopes AH visits F. Hilgendorf’s famous deposit [at Steinheim]. A. Weismann [Einfluss der Isolierung (1872)] makes good use of Hilgendorf’s observations.

Contributor:
Darwin Correspondence Project
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