182 OUTLINES OF EVOLUTIONABY BIOLOGY 



the habit of the plant, whether alpine or lowland, is really 

 inherited, or how far it may be produced afresh in each generation 

 as a direct response to environmental stimuli. 



It appears, however, from the observations of Bordage, 1 that 

 peach trees in the climate of Keunion gradually acquire an 

 almost evergreen habit, and that this character is hereditarily 

 transmitted, being exhibited by seedlings of the modified trees 

 when grown in situations where the peach is usually deciduous. 

 Dr. Bordage considers, and it appears to us that he has good 

 reason for so doing, that his observations and experiments defi- 

 nitely prove, in the case of plants, the hereditary transmission 

 of characters acquired under the influence of a change of climate. 



To take another example, it has been shown that in rats and 

 mice certain modifications in bodily structure are produced as the 

 result of raising or lowering the temperature to which the young 

 animal is exposed during its growth, and such modifications appear 

 to be inherited. Sumner 2 found, as the result of a large number 

 of careful measurements, that mice reared in a warm room (about 

 21 C.) differed considerably from those reared in a cold room 

 (about 5 C.) as regards the mean length of the tail, foot and ear, 

 which were longer in the former than in the latter. The same 

 differences occurred to a recognizable extent in the offspring of 

 the warm room and cold room parents, although these offspring 

 were all reared together in a common room under identical 

 temperature conditions. 



Observations such as these, which are rapidly accumulating, 

 lead us to hope that the question of the inheritance or non- 

 , inheritance of somatogenic characters which have undoubtedly 

 arisen in response to the direct action of the environment 

 may, before long, be answered conclusively. They doubtless require 

 confirmation and extension, but they afford very strong evidence 

 in favour of the inheritance of such characters. It has been sug- 

 gested that in such cases the stimulus of changed conditions affects 

 the body and the germ cells simultaneously and in a parallel 

 manner, rather than that the body is modified first and then in- 

 fluences the germ cells, but such a suggestion seems like a last 

 attempt to avoid at all costs the necessity for believing in the j 



1 Edmond Bordage, "A propos de 1'he'redite des caracteres acquis " (Bulletin 

 Scientifique dela France et de la Belgique. Tome XLIV, Paris, 1910). 



2 Francis B. Sumner, "An Experimental Study of Somatic Modifications and 

 their Reappearance in the Offspring," (Archiv fiir Entwicklungsmechanik der 



Organismen, Bd. 80, 1910). 



