332 On th e Xcsf mid Eggi^ of the Com in on Ter n 
TABLE XIX. 
Direct Homotyposis in Size and Shape. 
Characters 
Symbols 
Season 1913 
Season 1914 
Lengths of Eggs 
Breadths of Eggs 
Longitudinal Girths... 
Equatorial Girths 
z, z 
B, B 
Or, Gt 
Gi, G], 
•4643+ -0346 
•5176+ -0326 
. -.5076+ ^0327 
•4621 ± ^0350 
•60.56 ±-0107 
•7327+ -0078 
•6689 + -0093 
■7469± ^0075 
Index. 
100 BjL, 100 BjL 
•5537 ± •0308 
•5327 ±-0120 
It must at once be admitted that this result is of a very startling character. 
Only the homotyposis of the Index has remained without any significant change, 
i.e. the degree of likeness in shape does not exhibit a seasonal change ; in all four 
cases of absolute size there are most substantial and of course significant changes 
in the homotyposis. The mean size homotyposis has risen from '4879 to "6885, 
i.e. by about 40°/^! It is difficult to offer a demonstrable explanation of this 
great change. The factor we are seeking for must be one which modifies so to 
speak the individuality of the bird between its successive egg layings. For 
example, a change in the climatic condition or in the food supply occurring in 
1913 somewhere during the egg-laying period. Such a factor, however, would 
lead us to suppose that the high values of 1914 were the normal horaotypic 
values, whereas they appear to us from the comparative standpoint to be the 
abnormal. If we suppose only the stronger birds survived to the season 1914 and 
that there was a plentiful food supply, it would seem that the community as a 
whole should have exhibited less individuality in size and not more, — the weaker 
birds obtaining less food supply would not appear. Tliere is, however, so little 
change of type and variability of the eggs in the two seasons that it is hard 
to believe that selection of the birds is the source of the change. Further if 
anything the variability of the eggs is less in 1914 than 1913, and such reduction 
of variability would tend to reduce rather than increase correlation. If we suggest 
that 1913 killed off many of the old birds and that there was a larger proportion 
of young birds in 1914, so that there was a more heterogeneous community 
in 1914, we are pulled up by the fact that the eggs were on the average very 
slightly larger in 1914, which is, perhaps, not what we should anticipate with a 
larger proportion of first layers. It would seem as if we had to take refuge in 
some very vague statement that the seasonal environment for 1914 interfered 
less with individuality than that of 1913. But this does not really help us and 
leaves us with the greater difficulty, that it suggests that 'individuality' is an 
indefinite quantity from the statistical side and might result under favourable 
environmental conditions in all the eggs of a clutch being perfectly alike ! The 
persistency in the Index value seems in itself to point to a limitation in in- 
dividuality, and it seems wisest at present to await further material before 
