IV] 



STRUCTURE OF THE CELL 



181 



remarks: "This behaviour 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 also probable .that surface- 

 tensions between the particles and the surrounding protoplasm 

 would bring about an identical result, and would sufficiently 

 account for the obvious, and at first sight, very curious, symmetry. 

 We know that if we float a couple of matches in water they tend 

 to approach one another, till they lie close together, side by side ; 

 and, if we lay upon a smooth wet plate four matches, half broken 

 across, a precisely similar attraction brings the four matches 

 together in the form of a svmmetrical cross. Whether one of 

 these, or some other, be the actual explanation of the phenomenon, 

 it is at least plain that by some physical cause, some mutual and 



-Fig. 53. Annular chromosomes, formed in the spermatogenesis of 

 the Mole-cricket, (From Wilson, after Vom Rath.) 



symmetrical attraction or repulsion of the particles, we must seek 

 to account for the curious symmetry of these so-called '"tetrads." 

 The remarkable annular chromosomes, shewn in Fig. 53, can also 

 be easily imitated by means of loops of thread upon a soapy film 

 when the film within the annulus is broken or its tension reduced. 



So far as we have now gone, there is no great difficulty in 

 pointing to simple and familiar phenomena of a field of force 

 which are similar, or comparable, to the phenomena which we 

 witness within the cell. But among these latter phenomena 

 there are others for which it is not so easy to suggest, in accordance 

 with known laws, a simple mode of physical causation. It is not 

 at once obvious how, in any simple system of symmetrical forces, 



