J. de Meyer put the spermatozoa of sea urchins into sea water containing an extract of the eggs of the same species but found only that the spermatozoa swell in such a solution. Loeb and Bancroft made extensive experiments in cultivating spermatozoa of fowl _in vitro_ on suitable culture media. In yolk and white of egg the head of the spermatozoön underwent transformation into a nucleus, but no mitosis or aster formation was observed.[115] These experiments should be continued. [115] Loeb, J., _Artificial Parthenogenesis and Fertilization_, Chicago, 1913. CHAPTER VI DETERMINISM IN THE FORMATION OF AN ORGANISM FROM AN EGG 1. The writer in a former book (_Dynamics of Living Matter_, 1906, p. 1), defined living organisms as chemical machines consisting chiefly of colloidal material and possessing the peculiarity of preserving and reproducing themselves. Some authors like Driesch, and v. Uexküll seem to find it impossible to account for the development of such machines from an undifferentiated egg on a purely physicochemical basis. A study of Driesch’s very interesting and important book[116] shows that he assumes the eggs of certain animals, _e. g._, the sea urchin, to consist of homogeneous material; and he concludes that nature has solved, in the formation of highly differentiated organisms from such undifferentiated material, a problem which does not seem capable of a solution by physicochemical agencies alone. But the supposition of a structureless egg is wrong, since Boveri has demonstrated the existence of a very simple but definite structure in the unfertilized egg of the sea urchin; and a similar simple structure has been demonstrated by other authors, especially Conklin, in the eggs of other forms. [116] Driesch, H., _Science and Philosophy of the Organism_. London, 1908 and 1909. In this chapter we shall attempt the task among others of showing how, on the basis of the simple physicochemical structure of the unfertilized egg, the main organ of self-preservation of the organism, the intestine, is formed through the mere process of cell division and growth. Cell division is the most general of the specific functions of living matter and it is the basis underlying the differentiation of the comparatively simple structure of the egg into a more complex organism. If cell division and growth were equal in all parts of the egg no differentiation would be possible, but the different regions of the unfertilized egg contain different constituents and these, probably on account of their chemical difference, do not all begin to grow or divide simultaneously and equally.