314 



ON THE INTERNAL FORM 



[CH. 



The particles ir^y be rounded or linear, straight or bent, sometimes 

 annular; they may be all alike, or one or more may differ from 

 the rest. Lying as they do in a semi-fluid medium, and subject 

 (doubtless) to some symmetrical play of forces, it is not to be 

 wondered at that they arrange themselves in a symmetrical con- 

 figuration; and the field of force seems simple enough to let us 

 predict, to some extent, the symmetries open to them. We do not 

 know, we cannot safely surmise, the nature of the forces involved. 

 In discussing Brauer's observations on the sphtting of the chromatic 

 filament, and on the symmetrical arrangement of the separate 

 granules, in Ascaris megalocephala, LiUie* remarks: "This behaviour 



Fig. 94. Chromosomes, undergoing splitting and separation. 

 After Hatsehek and Flemming, diagrammatised. 



is strongly suggestive of the division of a colloidal particle under 

 the influence of its surface electrical charge, and of the effects of 

 mutual repulsion in keeping the products of division apart." It is 

 probable that surface-tensions between the particles and the sur- 

 rounding protoplasm would bring about an identical result, and 

 would sufficiently account for the obvious, and at first sight very 

 curious symmetry. If we float a couple of matches in water, we 

 know that they tend to approach one another till they He close 

 together, side by side; and if we lay upon a smooth wet plate 

 four matches, half broken across, a similar attraction brings the 

 four matches together in the form of a symmetrical cross. Whether 

 one of these, or yet another, be the explanation of the phenomenon, 



* R. S. Lillie, Conditions determining the disposition of the chromatic filaments, 

 etc., in mitosis; Biol. Bulletin, viii, 1905. 



