THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 237 



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

 the two sets arose by division ol' the sixteen mother-chromosomes. 

 Let us call the chromosomes a, h, r, 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-h migrated to the upper 

 pole of the spindle and l-q to the lower pole, then the miion of K a 

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

 present. In consideration of this I predicted to Dr. Petrunkewit?ch 

 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 theory. It majr, of course, be objected that the assumed 

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

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

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

 degree. Moreover, what other intei-pretation of the unexpected 

 development of the germ-cells discovered bj^ Petrunkewitseh could 

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

 vidual differences 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 gerl^l-cell formation is instituted, 

 after lialf the ids have been irrecoverably withdrawn from the 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. 



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