In a second paper, published in the following year, Driesch extended his experiments, and attempted to discover how far the “independence” of the blastomeres extends; _i.e._ he tried to find out if all the blastomeres resulting from the cleavage are alike. When one of the first four cells is separated from its fellows by shaking, it continues to divide, in most cases as a quarter, and produces later a small spherical blastula. Many of these blastulæ, although apparently healthy, never develop further, although they may remain alive for several days. In one experiment only eight out of twenty-six reached the pluteus stage, with a typical digestive tract and skeleton. From these experiments Driesch drew the important conclusion that the cleavage cells or blastomeres of the sea-urchin’s egg are equivalent, in the sense that if they were interchanged a normal embryo would still result. A somewhat similar view is expressed in the dictum that the position of a blastomere in its relation to the others determines what part it will produce, if its position is changed it gives rise to another part, etc.,--or, expressed more concisely, the prospective value of a blastomere is a function of its position.[115] Driesch extended these experiments further in 1893. His aim was to separate different groups of cells at the sixteen-cell stage in order to see whether the cells around the micromere pole (or “animal pole”) if separated from those of the opposite (or “vegetative pole”) could produce a whole embryo, etc. Eggs whose membranes had been removed by shaking immediately after fertilization were allowed to develop normally to the sixteen-cell stage and were then shaken into pieces. Amongst the groups of cells that were present those that contained the micromeres were picked out. It was found that they give rise to whole embryos. In order to obtain cells that belong to the vegetative hemisphere, the blastomeres were shaken apart at the eight-cell stage, and those groups of cells that in later divisions did not produce micromeres were isolated. From these also whole embryos develop. The results show that the cells of both hemispheres are able to produce whole embryos, and that at the sixteen-cell stage the different parts of the egg are still capable of producing all parts of the embryo. It is important to observe that the results of the experiment do not show that if the normal development goes on undisturbed any part of the egg may become any part of the embryo, for it is highly probable that a definite region of the egg may always produce a definite part of the embryo. The results do show, however, that, even if this is true, any cell has the power of producing any or all parts of the embryo if the normal conditions are changed.