LIFE IN ITS LOWER AND HIGHER FORMS 31 



minute network of very delicate fibrils, and an 

 apparently homogenous substance which occupies the 

 interstices of the network. 1 This is the basis of all 

 life. By reference to this AVC are led to contemplate 

 the two kingdoms, vegetable and animal, as one, for 

 there is an essential correspondence between the 

 elementary tissues of plants and animals. 2 These two 

 kingdoms, the one earlier, the other later, are the 

 outcome of the material energies working in the 

 natural history of the earth. With microscopic 

 examination of protoplasm and the formation of a 

 theory of cell-life, a promising beginning was made 

 for interpretation of this history. The range of 

 promise became apparent, when Theodore Schwann 

 reached the conclusion that there is one universal 

 principle of development for the elementary parts of 

 organisms, however different, and this principle is the 

 formation of cells. 3 



A living cell is a nucleated mass of protoplasm, 

 with or without a membrane for enclosure. It is 

 not infrequently a closed vesicle, and may vary from 

 _i_ to s i y of an inch in diameter. Such cells 

 constitute the basis from which the individual life 

 in the world is built up. Each cell contains a nucleus 

 which is an elementary organ, the active life-pro 

 pagating agency; and still within this, there is a 

 nucleolus which is the minute vital centre of action. 

 Living material, even in its primary form of utmost 

 simplicity, is thus strikingly complex. This living 



1 The Cell Theory, past and present. Inaugural address to the 

 Scottish Microscopical Society, by Professor Sir William Turner, 

 D.C.L., President, 1890, p. 27. 



2 Ibid., p. 11. 



3 Microskopische Untersuchungen, 1839. 



