18591863] FRENCH TRANSLATION 2OI 



generally have much restricted ranges, for this almost implies Letter 137 

 rapid change. What a curious case is offered by land-shells, 

 which become modified in every sub-district, and have yet re- 

 tained the same general structure from very remote geological 

 periods ! When working at the Glacial period, I remember 

 feeling much surprised how few birds, no mammals, and very 

 few sea-mollusca seemed to have crossed, or deeply entered, 

 the inter-tropical regions during the cold period. Insects, 

 from all you say, seem to come under the same category. 

 Plants seem to migrate more readily than animals. Do not 

 underrate the length of Glacial period : Forbes used to argue 

 that it was equivalent to the whole of the Pleistocene period 

 in the warmer latitudes. I believe, with you, that we shall be 

 driven to an older Glacial period. 



I am very sorry to hear about the British Museum ; it 

 would be hopeless to contend against any one supported by 

 Owen. Perhaps another chance might occur before very long. 

 How would it be to speak to Owen as soon as your own mind 

 is made up ? From what I have heard, since talking to you, 

 I fear the strongest personal interest with a Minister is requisite 

 for a pension. 



Farewell, and may success attend the acerrimo pro- 

 pugnatori. 



P.S. I deeply wish you could find some situation in 

 which you could give your time to science ; it would be a 

 great thing for science and for yourself. 



To J. L. A. de Ouatrefages. Letter 138 



Down, July nth [1862]. 



I thank you cordially for so kindly and promptly answer- 

 ing my questions. I will quote some of your remarks. 

 The case seems to me of some importance with reference 

 to my heretical notions, for it shows how larvae might be 

 modified. I shall not publish, I daresay, for a year, for much 

 time is expended in experiments. If within this time you 

 should acquire any fresh information on the similarity of the 

 moths of distinct races, and would allow me to quote any 

 facts on your authority, I should feel very grateful. 



I thank you for your great kindness with respect to the 

 translation of the Origin ; it is very liberal in you, as we 



