Summary

Obliged for letter on worm-castings. Asks GK to observe them in southern Europe.

Summary

Sends a copy of Expression and his autograph.

Summary

Sends a copy of Expression

and speaks fondly of his memories of Woodhouse and the Owen family.

Summary

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.