INSECTS
highly disconcerting event if it happened anywhere else than in a termite colony, where it is the regular thing. But the fact of its being regular with termites makes it none the less disconcerting to entomologists, for it seems to defy the very laws of heredity.
There can be no doubt of the utility of a caste system where the members of each caste know their places and their duties, and where nobody ever thinks of starting a social revolution. But we should like to know how such a system was ever established, and how individuals of a family are not only born different but are made to admit it and to act accordingly.
These are abstruse questions, and entomologists are divided in opinion as to the proper answers. Some have maintained that the termite castes are not distinguished when the various individuals are young, but are produced later by differences in the feeding—in other words, it is claimed the castes are made to order by the termites themselves. One particular objection to this view is that no one has succeeded in finding out what the miraculous pabulum may be, and no one has been able to bring about a structural change in any termite by controlling its diet. On the other hand, it has been shown that in some species there are actual differences in the young at the rime of hatching, and such observations establish the fact that insects from eggs laid by one female can, at least, give rise to offspring of two or more forms, beside those of sex, and that potential differences are determined in the eggs. It is most probable that in these forms no structural differences could be discovered at an early embryonic period, and hence it may be that, where differences are not perceptible at the time of hatching, the period of differentiation has only been delayed to a later stage of growth. It is possible that a solution to the problem of the termite castes will be found when a study of the eggs themselves has been made.
We may conclude, therefore, that the structural differ-
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