KARYOKINESIS 



9i 



"The spindle of which we give a photograph in Fig. 31 

 was made by placing in salt water a drop of the same solution 

 pigmented with blood or Indian ink, and placing on either 

 side of this central drop a hypertonic drop of salt solution 

 more lightly coloured. After diffusion had gone on for some 

 minutes, we obtained the figure which we have photographed. 

 I would draw your attention to the equatorial plane, which 

 shows that the spindle is not formed by lines of force passing 

 from one pole to the other, as would be the case between two 

 poles of contrary sign, but by two forces acting in opposite 

 directions. On either side the pigment of the central drop 



Fig. 31. — Diffusion figure representing karyokinesis. Achromatin spindle 

 between two similar poles of concentration. 



has been drawn towards the hypertonic centre nearest to it. 

 In the median line, however, the pigment is attracted in 

 opposite directions by equal forces, and therefore remains 

 undisturbed, marking the position of the equatorial plane. 

 This observation applies equally to the equatorial plane 

 in natural karyokinesis, whose existence is thus readily ex- 

 plained. 



"It is hardly necessary to insist on the fact that liquid 

 preparations like these are of extreme delicacy and sensitive- 

 ness, and require for their production, and still more for their 

 photography, the greatest care and skill, which can only be 

 acquired by long practice. 



