But even though we may assume that there is a similar difference in the mode of feeding among most ants, because the workers are considerably smaller than the fertile females, it would be quite erroneous to conclude that the difference between the two types rests solely on the effect of differences in diet. The elimination of an individual organ has never yet been determined by bad and scanty nourishment; it is the whole animal with all its parts that degenerates and becomes small and weakly. Often as caterpillars of different species have been placed on starvation diet, whether for experimental purposes or to procure very small butterflies, it has never yet happened that a single organ, such as antenna, leg, or wing, has thereby been eliminated or caused to degenerate. I have myself instituted many such experiments with the maggots of the blue-bottle fly, by supplying them from their earliest youth with just as little food as possible without actually starving them to death, yet never have these larvæ given rise to flies in which the wings were absent or rudimentary. Nor did these starved flies ever exhibit degenerate ovaries; they were always completely developed and equipped with the full number of ovarian-tubes. It was to decide this particular point that these experiments were instituted, for my opponents maintained that degeneration of the ovaries was a direct result of inferior nourishment. But that is not the case. Special investigations in regard to ants, undertaken at my request by Miss Elizabeth Bickford, showed that the anatomical results reached by earlier investigators, like Adlerz and Lespès, in regard to the degeneration of the ovaries in workers, were absolutely correct, and that the 'degeneration' consists not merely in the fact that the ovarian-tubes and ovum-primordia remain small, but also in a diminution of the _number_ of ovarian-tubes (Fig. 105); the workers have always fewer ovarian-tubes than the females of the same species, and--what is of especial importance--the reduction in the number of ovarian-tubes has been effected to a different extent in different species of ants. In the red wood-ant (_Formica rufa_) the workers still possess from twelve to sixteen ovarian-tubes; in the meadow-ant (_Formica pratensis_) only eight, six, or four; in _Lasius fuliginosus_ there are usually only two (one on either side); and in the little turf-ant (_Tetramorium cæspitum_) there are none at all. We have here, therefore, a phylogenetic process of degeneration, which has reached different degrees in the different species, and has only been completed in one (_Tetramorium_). The case stands as I previously stated it: 'The elimination of a typical organ is not an ontogenetic process, but a phylogenetic one,' it depends not upon 'the mere influences of nutrition which affect the development of the individual, but always on variations in the germ-plasm, which, to all appearance,