IV] AND STRUCTURE OF THE CELL 337 



The problem recalls the famous problem of three bodies, which has 

 so occupied the astronomers; and it is obvious that the foregoing 

 brief description is very far from including all possible cases. 

 Many of these are particularly described in the works of Fol, Roux, 

 Whitman and others*. 



The intracellular phenomena of which we have now spoken have 

 assumed great importance in biological literature and discussion 

 during the last fifty years; but it is open to us to doubt whether 

 they will be found in the end to possess more than a secondary, 

 even a remote, biological significance. Most, if not all of them, 

 would seem to follow immediately and inevitably from certain 

 simple assumptions as to the physical constitution of the cell, and 

 from an extremely simple distribution of polarised forces within it. 

 We have already seen that how a thing grows, and what it grows 

 into, is a dynamic and not a merely material problem; so far as 

 the material substance is concerned, it is so only by reason of the 

 chemical, electrical or other forces which are associated with it. 

 But there is another consideration which would lead us to suspect 

 that many features in the structure and configuration of the cell 

 are of secondary biological importance; and that is, the great 

 variation to which these phenomena are subject in similar or closely 

 related organisms, and the apparent impossibihty of correlating 

 them with the pecuHarities of the organism as a whole. In a 

 broad and general way the phenomena are always the same. Certain 

 structures swell and contract, twine and untwine, split and unite, 

 advance and retire ; certain chemical changes also repeat themselves. 

 But Nature rings the changes on all the details. "Comparative 

 study has shewn that almost every detail of the processes (of 

 mitosis) described above is subject to variation in different forms 

 of cells |." A multitude of cells divide to the accompaniment of 

 caryokinetic phenomena; but others do so without any visible 

 caryokinesis at all. Sometimes the polarised field of force is within, 



* H. Fol, Becherches sur la fecondation, 1879; W. Roux, Beitrage zur Erit- 

 wickelungsmechanik des Embryos, Arch. f. Mikr. Anat. xix, 1887; C. 0. Whitman, 

 Ookinesis, Journ. Morph. i, 1887; E. Giglio-Tos, Entwicklungsmechanische 

 Studien, I, Arch. f. Entw. Mech. li, p. 94, 1922, See also Frank R. Lillie, Problems 

 of Fertilisation, Chicago, 1919. 



t Wilson, The Cell. p. 77; cf. 3rd ed. (1925), p. 120. 



