question of adaptation in general, and I think it highly probable that it will prove true that there are many kinds of adaptive responses that must be considered separately and each on its own merits. Let us, therefore, confine our concluding remarks entirely to _regenerative changes_ which, after they have been completed, are for the good of the organisms. Our preceding discussion has led to the conclusion that the phenomena of regeneration are not processes that have been built up by the accumulation of small advances in a useful direction; that they cannot be accounted for by the survival of those forms in which the changes take place better than in their fellows, for it is often not a question of life and death whether or not the process takes place, or even a question of leaving more descendants. On the contrary, it seems highly probable that the regenerative process is one of the fundamental attributes of living things, and that we can find no explanation of it as the outcome of the selective agency of the environment. The phenomena of regeneration appear to belong to the general category of growth-phenomena, and as such are characteristic of organisms. Neither regeneration nor growth can be explained, so far as I can see, as the result of the usefulness of these attributes to the bodies with which they are indissolubly associated. The fact that the process of regeneration is useful to the organism cannot be made to account for its existence in the organism. LITERATURE =Aldrovandus, Ulysses.= 1642. Historia Monstrorum. MDCXLII. Cap. VIII. 1645. Patritii boloniensis de quadrupedibus digitatis oviparis. Lib. II. Boloniae, MDCXXXXV. =Allman, J. A.= ’64. Report of the present State of our Knowledge of the Reproductive System in the Hydroida. Report of the 33d Meeting of the British Assoc., 1864. =Andrews, E. A.= ’90. Autotomy in the Crab. The American Naturalist, XXIV, 1890. ’91. Report upon the Annelida Polychaeta of Beaufort, North Carolina. Proc. U. S. National Museum, XV, p. 286, 1891. =Andrews, G. F.= ’97. Some Spinning Activities of Protoplasm, etc. Jour. Morph., XII, 1897. =Apostolides, N. Christo.= ’82. Anatomie et développement des Ophiures. Arch. Zool. Expérim., X, 1882. =Aristotle.= Historia de animalibus, Julio Caesare, Scaligero interprete, cum ejusdem Commentariis. Tolosae, MDCXIX, Lib. II, Cap. XX. =Arnoult de Nobleville et Salerne.= 1756. Suite de la matière médicale de Geoffroy, t. 12, MDCCLVI. =Aschoff, L.= ’95. Regeneration und Hypertrophie. Ergebnisse d. allg. Path. Morph. und Physiol., 1895. =Balbiani, E. G.= ’88. Recherches expérimentales sur la mérotomie des infusoires ciliés. Recueil zool. de la Suisse, V, 1888. ’91. Sur les régénérations successives du peristome, etc., chez les stentors, etc. Zool. Anz., 1891. ’91. Nouvelles recherches expérimentales sur la mérotomie des infusoires ciliés. Arch. microgr., IV et V, 1891-93.