An Experimental Study of Somatic Modifications etc. 333 
external conditions to which they had been subjected? Unfortunately, 
the data necessary for a satisfactory answer to this question are not at 
hand, since, in the case of the parents of this particular lot, only 
the weight and tail length were determined at the age of six weeks 
We may, however, make this comparison in respect to tail length. 
Fig. 6. 
7 8 9 -10 11 12 13 15 16 17 18 19 
Curves showing tail length, at 42 days, of the offspring of modified parents, reared under conditions 
identical for all. The heavy line(VF) represents the condition in the offspring of warm-room parents, 
the lighter line (C) representing the condition in the offspring of cold-room parents. Ahscissas denote 
weigth in grams; ordinates denote tail length in millimeters. The figures along the curves denote the 
number of individuals in each size-group. 
An inspection of Figures 2 and 6 shows at once that this difference 
has very much diminished in the second generation. 
It will likewise be instructive to compare the the mean differ- 
ences shown by parents and offspring in respect to this character. 
1) See above. 
