To J. D. Hooker 27 [June 1854]
Down Farnborough Kent
My dear Hooker
I send you very sincere congratulations on your affair being over, in which my wife very truly joins.— You seem to have taken it very philosophically. In my opinion these affairs, like gales of wind, get less & less endurable.
Did you administer the Chloroform? When I did, I was perfectly convinced that the Chloroform was very composing to oneself as well as to the patient.1
I, like you, am reading Brodies book with very lively interest.2
With respect to “highness” & “lowness”, my ideas are only eclectic & not very clear. It appears to me that an unavoidable wish to compare all animals with men, as supreme, causes some confusion; & I think that nothing besides some such vague comparison is intended, or perhaps is even possible, when the question is whether two kingdoms such as the articulata or mollusca are the highest. Within the same kingdom, I am inclined to think that “highest” usually means that form, which has undergone most “morphological differentation” from the common embryo or archetype of the class; but then every now & then one is bothered (as Milne Edwards has remarked) by “retrograde development”,3 ie the mature animal having fewer & less important organs than its own embryo.4 The specialisation of parts to different functions, or “the division of physiological labour” of Milne Edwards exactly agrees (& to my mind is the best definition, when it can be applied) with what you state is your idea in regard to plants. I do not think zoologists agree in any definite ideas on this subject; & my ideas are not clearer than those of my Brethren.5
Ever yours, C. Darwin
Give my kindest remembrances to all at Hitcham.
I enjoyed my dinner very much at the Club though I was a good deal tired.—
CD gives his definition of "highness" and "lowness" as "morphological differentiation" from a common embryo or archetype. JDH’s view, with which CD agrees when it can be applied, is the same as Milne-Edwards’, i.e., the physiological division of labour. There is little agreement among zoologists and CD admits his own lack of clarity.