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From Alpheus Hyatt   January 1877


Reports on his work. Relationships of shells found at Steinheim; attempts to elucidate the genesis of different forms.

Author:  Alpheus Hyatt
Addressee:  Charles Robert Darwin
Date:  Jan 1877
Classmark:  DAR 166: 357, 359
Letter no:  DCP-LETT-10760

From Alpheus Hyatt   23 May 1881


Wishes to correct impression of his attitude towards CD’s contribution: CD has successfully explained how differences arise.

Pleased CD will read his book [Tertiary species of Planorbis at Steinheim (1880)].

Author:  Alpheus Hyatt
Addressee:  Charles Robert Darwin
Date:  23 May 1881
Classmark:  DAR 166: 360
Letter no:  DCP-LETT-13171

From Alpheus Hyatt   [late] November 1872


No need to apologise for not quoting AH’s paper on acceleration and retardation.

Agassiz introduced AH to ammonites and entrusted collection to him. Has followed developmental history of each species and placed them within geological formations. Found evolutionary history of species recapitulated only to a degree in individual development. Stages frequently skipped. Explains why young of later animals are like adults that preceded them. Retardation entirely idea of Edward Drinker Cope. Sends paper to explain it. Acceleration can explain degraded forms. Often like youthful stage with which series began. Often resemble old age of earlier series. Regularity of these series incompatible with natural selection. How can selection account for degraded final stages or for predictability of development? Franz Hilgendorf’s Paludinae from Steinheim lake show same parallelism in development. May be possible to reconcile this with selection. But Trochiformis begins to show degradation in beds where it is most numerous and has largest individuals, i.e., where selection seems to be favouring it. Will work on Steinheim shells this winter.

Author:  Alpheus Hyatt
Addressee:  Charles Robert Darwin
Date:  [late] Nov 1872
Classmark:  DAR 99: 48–55
Letter no:  DCP-LETT-8655

From Alpheus Hyatt   8 December 1872


Discusses his theory of acceleration and retardation of development.

Author:  Alpheus Hyatt
Addressee:  Charles Robert Darwin
Date:  8 Dec 1872
Classmark:  DAR 145: 365
Letter no:  DCP-LETT-8665

From Alpheus Hyatt   8 January [1875]


Encloses report on his paper "Old age characteristics among ammonites", [Proc. Boston Soc. Nat. Hist. 17 (1875): 236–41].

Stability of long inherited characters. Dependence of some recently acquired characters on the environment.

Author:  Alpheus Hyatt
Addressee:  Charles Robert Darwin
Date:  8 Jan [1875]
Classmark:  DAR 166: 358
Letter no:  DCP-LETT-9233
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letter (5)
Darwin, C. R.disabled_by_default
Darwin, C. R.disabled_by_default
Hyatt, Alpheusdisabled_by_default
1872 (2)
1875 (1)
1877 (1)
1881 (1)