No. 2.] OOKINESIS, 231 



tive indication of any action whatever between the two pronuclei. 

 Now this action, which we may call centripetal attraction for 

 want of a more definite term, is, as before stated, all that is re- 

 quired to account for the centripetal movement of the pronuclei. 

 But would this movement result in bringing the pronuclei to- 

 gether? Evidently it would, if the attraction was the same for 

 each pronucleus. 



Wherein, then, lies the evidence of attraction between the 

 pronuclei? In order to elucidate this question let us consider 

 how such a force would manifest itself in the movements of 

 these bodies. We should have two forces, one tending to 

 bring the pronuclei together in a direction marked by the chord 

 joining them, the other tending to draw them along their re- 

 spective radii to the centre of the ^%^. The place of meeting 

 and the nature of the lines described by the pronuclei will de- 

 pend on a variety of circumstances. Prominent among these 

 are \\\e: place and tijjie of origin. The probability that neither 

 of these forces acts uniformly throughout, and the possibility 

 that the attraction between the pronuclei may act only within 

 shorter distances than those by which these bodies are often 

 separated, will have to be taken into account. 



To begin with, let us suppose that the pronuclei are contem- 

 poraneous in origin and located at opposite poles. A typical 

 illustration of such conditions is furnished in the nematode egg. 

 The component forces would here act in 

 the same direction and drive the pronuclei 

 straight to the point of meeting (<:). The 

 possibility of meeting at the centre would 

 depend upon the obvious conditions, — (i) 

 that they start at the same moment and 

 move with equal velocity, or (2) that any 

 difference in one of these respects is neu- 

 tralized by a counter difference in the 

 other. 



If the starting-points (/;/ and f, Fig. 2) 

 were near the same pole, the other conditions remaining the 

 same, the place of meeting (or) would be eccentric, and the na- 

 ture of the paths described would, of course, depend on the 

 relation sustained between the component forces. If this rela- 

 tion is uniform, the pronuclei will move in straight lines to the 



