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.
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.
I, like you, am reading Brodies book with very lively interest.
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”, ie the mature animal having fewer & less important organs than its own embryo. 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.
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.—
- f1 1573.f1See Correspondence vol. 4, letter to W. D. Fox, [17 January 1850] and n. 3.
- f2 1573.f2[Brodie] 1854. See letter from J. D. Hooker, [24 June 1854], and letter to Josiah Wedgwood III, 1 May , n. 2.
- f3 1573.f3Henri Milne-Edwards advanced the principle of the ‘division of physiological labour’ as a means to assess structural complexity in an organism. Morphological differentiation characterised by a division and distribution of functions was considered an indication of higher organisation. Those organisms which showed ‘retrograde development’, where the mature form is less differentiated than the larva or embryo, he believed resulted from arrested development, and he laid great emphasis on this criterion in classification (Appel 1987, pp. 216–22). These ideas were expressed in his influential memoir on the natural classification of animals (Milne-Edwards 1844), which CD read in December 1846 and abstracted (DAR 72: 117–22). See Correspondence vol. 4, Appendix II.
- f4 1573.f4As in the males and complemental males of Cirripedia (see Living Cirripedia (1851): 282).
- f5 1573.f5CD had been concerned with the problem of defining ‘higher’ and ‘lower’ since at least 1843 (see Correspondence vol. 2, letter to G. R. Waterhouse, [31 July 1843]). The view generally held by naturalists at the time, drawn from embryology, was that an advance from lower to higher organisms was an advance from the more general to the more special form (see Ospovat 1981, pp. 216–28 and Appel 1987, pp. 216–22). CD's views on highness and lowness in the particular context of ranking the Cirripedia were discussed in Living Cirripedia (1854): 19–20. He specifically mentioned James Dwight Dana's criterion of ‘the greater or less centralisation of all the appendages round the mouth’ and Karl Ernst von Baer's idea of ‘morphological differentiation’. Although stating that this, ‘as it seems to me, is a very obscure enquiry’, he concluded by offering his own view (p. 20): |cil2cir1| On the whole, I look at a Cirripede as a being of a low type, which has undergone much morphological differentiation, and which has, in some few lines of structure, arrived at considerable perfection,—meaning, by the terms perfection and lowness, some vague resemblance to animals universally considered of a higher rank.