80 Hypothesis of Structure of Germ Substance 
writes Strassburger, “it is absolutely impossible to hunt 
out anything but equal division. Unequal division is not 
presented at all. There is not a single fact to support the 
notion that it exists.” °° 
We shall here limit ourselves to mentioning only two 
orders of facts which speak directly against unequal divi- 
sion: 
First, it does not occur in any nucleus in the vast realm 
of unicellular and of primitive pluricellular forms, con- 
sisting of colonies of like cells; for in them the facts of 
heredity show directly that nuclear division is always 
equal. 
But especially the oft repeated and keenly discussed 
experiments upon the relative shifting and isolation of 
blastomeres afford direct proof that nuclear division is 
equal in the first segmentations of the egg. We recall for 
éxample the experiments of Chabry upon the Ascidians, 
those of Wilson upon Amphioxus, those of Herbst on the 
separation of the blastomeres of the sea urchin merely by 
adding chloride of potassium to ordinary sea water, of 
Driesch on the Echinus microtuberculatus, of Oscar Hert- 
wig upon frogs’ eggs, of Raffaello Zoja on the Medusae 
and so on. These experiments in which one of the first 
blastomeres, or one of the four, or eight, or sixteen, or 
thirty-two first blastomeres, produce when isolated an 
entire embryo, perfectly formed but proportionally 
smaller, or in which the blastomeres, though shuffled 
about in any way whatever, nevertheless developed in a 
perfectly normal way, lead with the greatest certainty 
that any one could desire to the conviction that in the 
°StraBburger: Uber periodische Reduktion der Chromosomen- 
zahl im Entwicklungsgang der Organismen. Biol. Centralbl., XIV. 
No. 23-24. Leipzig, Dec. 1, and 15, 1894. P. 835. 
