Smallest total length, 1.2 cm. body, 0.5 " tail, 0.7 " Largest total length, 1.8 " body, 0.7 " tail, 1.1 " These last measurements were made after the tadpoles had been preserved in spirit, and were therefore doubtless somewhat less than in the fresh condition. Making allowance for this it is evident that the tails had undergone reduction as part of the metamorphosis, but the body was also shorter. There is some reason therefore for concluding that actual reduction in size of body occurs as the result of metamorphosis induced by thyroid feeding. As in the other case the skin and opercular membranes were distended by liquid beneath them. The total period of the change in this second experiment was ten days. I conclude that the amount of thyroid eaten was so excessive as to cause pathological conditions as well as precocious metamorphosis, so that the animals died without completing the process. On June 10 I still had four tadpoles which had never had thyroid, but only pieces of meat, earthworm, or fish. These were very much larger than any of the others, were active and vigorous, and the largest one showed small rudiments of hind-legs, the others none at all. CHAPTER VII Metamorphosis And Recapitulation As one of the most remarkable examples of metamorphosis and recapitulation in connexion with adaptation we will consider once more the case of the Flat-fishes which I have already mentioned in an earlier chapter. These fishes offer perhaps the best example of the difference between gametogenic mutations and adaptive modifications. In several species specimens occur occasionally in which the asymmetry is not fully developed. [Footnote: See 'Coloration of Skins of Fishes, especially of Pleuronectidae,' _Phil. Trans. Royal Soc_., 1894.] These abnormalities are most frequent in the Turbot, Brill, Flounder, and Plaice. The chief abnormal features are pigmentation of the lower side as well as of the upper, the eye of the lower side, left or right according to the species, on the edge of the head instead of the upper side, and the dorsal fin with its attachment ceasing behind this eye, the end of the fin projecting freely forwards over the eye in the form of a hook. Such specimens have been called ambicolorate, but it is an important fact that they are also ambiarmate--that is to say, the scales or tubercles which in the normal Flat-fish are considerably reduced or absent on the lower side, in these abnormal specimens are developed on the lower side almost as much as on the tipper. Minor degrees of the abnormality occur: in Turbot with the hook-like projection of the dorsal fin the lower side of the head is often without pigment, while the rest of the lower side is pigmented. Less degrees of pigmentation of the lower side occur without structural abnormality of the eye and dorsal fin.