THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 237 



two sets of sixteen chromosomes must have been quite similar, since 

 the two sets arose by division of the sixteen mother-chromosomes. 

 Let us call the chromosomes a, h, e, d-q, then similar sets of chromo- 

 somes must have been contained in the two nuclear spindle figures 

 depicted in Fig. 79 at the beginning of the division, and eight of these 

 went to each daughter-nucleus. Now, if a-k migrated to the upper 

 pole of the spindle and l-q to the lower pole, then the union of K 2 

 with K 3 would bring together again all the ids that had before been 

 present. In consideration of this I predicted to Dr. Petrunkewitsch 

 that this copulation-product might be the basis of the formation 

 of the germ-cells in the drone-bee, and his painstaking and difficult 

 researches have confirmed this prediction, strange though it may 

 seem, that the male germ-cells have a different origin from the 

 female germ-cells. But this discovery gives a strong support to the 

 germ-plasm theorj'. It may, of course, be objected that the assumed 

 regular distribution of the ids in the tAvo daughter-nuclei cannot 

 be proved, but we know already that this dividing apparatus does 

 very exact work, and we are at liberty to assume it in an even higher 

 degree. Moreover, what other interpretation of the unexpected 

 development of the germ-cells discovered by Petrunkewitsch could 

 be given if this had to be rejected 1 A clearer proof of the indi- 

 vidual dififerences of ids and of their essential importance could not 

 be desired, than lies in the fact that in the ' male ' eggs of the queen- 

 bee a different and novel mode of germ-cell formation is instituted, 

 after half the ids have been irrecoverably withdrawn from the 

 ovum-nucleus. We see from this that for individual development 

 a duplication of individual ids may suffice, but that for the further 

 development of the species a retention of the diversity of the ids 

 is important. 



