WCP4636

[1]

^Answ[ere]d1

University College Bristol²

28^th April 1891

Dear Mr Wallace

I have not forgotten the request you made that I should endeavour to suggest experiments on Use. inheritance. But I find such suggestions not altogether easy to make.

Satisfactory evidence of the inherited effects of increased use by itself will, I imagine, be difficult to obtain under experimental conditions; observations on the effects of disuse by itself would be complicated by the panmixia question. I should therefore suggest observations directed towards the inheritance of differential use as less open to these objections, & to the criticism that the effects might be due to the conditions of domesticity.

Would it not be possible to induce in domesticated animals or birds a lopsided development? If this were continued through [2] a series of generations, without any selection, it might be seen whether there was any tendency for this lopsidedness to be inherited. High action in the horse can be induced by weighting the limbs: I am not aware thi whether this has been done for a series of generations & whether there is any indication of such high action being inherited. By differential weighting a differential action might be established, & any hereditary tendency would be more readily observable. Preliminary experiments on rapidly breeding individuals would probably soon lead to indications of the most convenient form of continuing the experiments and observation[s?].

In lop-eared rabbits there is a decided twist or Set to the skull. There is no distinct evidence, at present whether this is due to correlated variation or to the inherited effects of the lop. It would be possible I suppose to induce a lop in other strains of rabbits, and perhaps in guinea pigs, by artificially weighting the left ear. A number of the rabbits or guinea pigs might be at the outset divided into two groups which should be kept as far as possible under similar conditions[.] [3] Except that in one set the left ear of each individual was kept permanently weighted. After four or five generations, certain individuals of the weighted group should be set aside, unweighted from their birth, and observed. While observations and measurements of the skulls of some of them should be made ^{and compared with those made of the skulls of individuals weighted from birth} and recorded. If it should be found that at the end of twenty or thirty generations, though the effects on the individual were well marked, there was no evidence of any inherited effect, each negative evidence would be pro tanto of value, while positive evidence obtained in this way does not seem to be open to damaging criticism.

You will see that the essence of my suggestion, which I cannot regard as very valuable, is that the observations should be directed to differential effects.

I have to give a presidential address to the Bristol Naturalists Society next week & have chosen as my subject the nature and origin of variations. Therein I shall make this suggestion and I may induce some of our members to cooperate with me in carrying out preliminary [4] Experiments on these lines. I would undertake general supervision & measurement of Skulls. Please let me know if there appear to you to be any reasons why such experiments should be considered unsatisfactory, impracticable, or inconclusive. If the principle be satisfactory others on similar lines will no doubt suggest themselves.

With apologies for delay in answering your letter a delay due to laziness following a spell of work and worry

Believe me| Yours very truly| C. Lloyd Morgan [signature]