2. ‘Observations on the Histology and Physiology of the Placenta of the Mouse.’ _Tijdschr. Nederland. Dierkund. Vereen._, vii (2). 1902. 3. ‘Observations on the Maturation and Fertilization of the Egg of the Axolotl.’ _Quart. Jour. Micr. Science_, xlviii. 1905. 4. ‘Remarks on the Germinal Layers of Vertebrates and on the Significance of Germinal Layers in general.’ _Mem. and Proc. Manchester Lit. and Phil. Soc._, 1906. 5. ‘Notes on the Histology and Physiology of the Placenta in Ungulata.’ _Proc. Zool. Soc._ 1906. 6. ‘On the Effects of certain Solutions upon the Development of the Frog’s Egg.’ _Arch. Ent.-Mech._, xxi. 1906. 7. ‘On the Relation between the Symmetry of the Egg and the Symmetry of the Embryo in the Frog (_Rana temporaria_).’ _Biometrika_, v. 1906. 8. _Experimental Embryology_. Oxford, 1909. 9. ‘On the Relation between the Symmetry of the Egg, the Symmetry of Segmentation, and the Symmetry of the Embryo in the Frog.’ _Biometrika_, vii. 1909. 10. ‘The Effects of Sodium Chloride on the Growth and Variability of the Tadpole of the Frog.’ _Arch. Ent.-Mech._, xxx (2). 1910. 11. ‘Vitalism.’ _Hibbert Journal_. 1911. 12. ‘On the Development of Isolated Pieces of the Gastrulae of the Sea-Urchin _Strongylocentrotus lividus_.’ _Arch. Ent.-Mech._, xxxii. 1911. 13. ‘On the Effect of certain Isotonic Solutions on the Development of the Frog.’ _Arch. Ent.-Mech._, xxxii. 1911. 14. ‘On the Origin of the Polar and Bilateral Structure of the Egg of the Sea-Urchin.’ _Arch. Ent.-Mech._, xxxii. 1911. 15. ‘The Development of the Ear-Bones in the Mouse.’ _Jour. Anat. and Phys._, vi (3). 1911. 16. ‘Growth, Variability, and Correlation in Young Trout.’ _Biometrika_, viii. 1912. 17. _Vertebrate Embryology_. Oxford, 1913. 18. ‘The Effect of Centrifugal Force on the Structure and Development of the Egg of the Frog.’ _Quart. Jour. Micr. Science._ 1914. 19. ‘The Placenta of a Lemur.’ _Quart. Jour. Micr. Science._ July 1915. 20. _Three Lectures on Experimental Embryology_. Oxford, 1917. VITALISM By J. W. Jenkinson In one of the oldest biological treatises in the world, the soul or life of an organism is defined in the most general way as an activity of a natural organic living body--ἐντελέχεια σώματος φυσικου̑ ὀργανικου̑ δυνάμει ζωὴν ἔχοντος--life being autonomous nutrition and growth and decay. The activity may, however, be latent or patent, passive or active, sleeping or waking, without losing its peculiar characters. It is substance (οὐσία), but substance as ‘form’ as opposed to the material substance of the body, and the living body is therefore also a substance in a double sense.