are differentiated into workers and queens. Frequently other castes, soldiers and others, are similarly recognisable. As regards formulation of his problem, Professor Pearson will perceive that the parallel to average homotyposis is not average fraternal correlation of even all the females from one pair of parents, but the correlation between workers, or between soldiers, &c., of one family. He may reply that this objection, though true on the point of form, can be met by weighting the various castes when they are compared. I doubt whether the difficulty is thus fully met (even if in practice it were possible to carry out the process). Should we even then be comparing comparables ?
Should we not still be finding a correlation like that for a miscellany of differentiated series of repeated parts 1
This reasoning, so clear in the case of Ants, extends to all cases of differentiation between members of confraternities.
To find then a value comparable with the homotyposis of undifferen- tiated like parts we must find the fraternal correlation between undifferentiated like brothers. But differentiation has here again no meaning which can be determined with precision. It shades insensibly into variation.
Suppose we merely propose to determine the arerafje value of fra- ternal correlation in workers of one genus of Ants. In some species we sort our Ants easily into workers and the rest. In another species we shall find differentiation so imperfect that we cannot say for certain which are soldiers and which workers. Finally, even in the more com- pletely differentiated species we shall find occasional nests (families) which show an imperfect differentiation.* Average fraternal correla- tion, I think, has no meaning, still less an ascertainable value, in these cases.
The principle that Professor Pearson calls " homotyposis " I have expressed by the statement that the variations of parts, repeated in series, may be " similar and simultaneous."! Beyond this we cannot yet go. Professor Pearson's statement of the principle fails to recognise one of the most important features of homotyposis. Expressed in mv own terms, Professor Pearson's " homotyposis " is the principle of " similar and simultaneous variation " restricted to undifferentiated likr parts.
But relationship is not lost when we pass to the differentiated parts, and such differentiated parts may vary similarly and simultaneous] y with other differentiated parts of the same series, exhibiting the phenomenon of Homceosis. A stamen of a Rose, if it becomes petaloid, is not merely a petal, but a petal of the individual Rose it is on. Professor Pearson's principle, as stated by him, misses this point.
If he had correctly instituted the comparison between parts and
- See the writings of Forel.
t ' Materials," p. 569.
