Errect oF Ions upon Tissue 565 
1, ON THE DIFFERENT EFFECTS OF IONS UPON UNDIFFER- 
ENTIATED EMBRYONIO TISSUE AND UPON MUSCLE 
While the method established in the preceding section 
may be successfully applied to all kinds of tissues, I was 
most interested to know whether there is a marked difference 
between undifferentiated embryonic and differentiated older 
tissue. By embryonic protoplasm or tissue I mean the early 
egg-cells, the growing regions in plants and animals, rapidly 
growing tumors, regenerating parts or organs, in short, cells 
which are characterized by rapid multiplication. If we are 
ever to build up a technical or constructive, in the place of 
a merely analytical, biology, we shall be able to do it on the 
basis of a more thorough knowledge of the character of 
embryonic matter. I tried to find out whether the various 
metal ions have the same effect upon the undifferentiated 
egg-cells as upon muscle. These experiments throw some 
light upon another problem. The karyokinetic cell-division 
has been identified with phenomena of muscular contraction. 
We shall see incidentally how far such an idea is justifiable. 
In my former experiments on development I was guided 
by the idea that the various morphological stages were 
preceded by chemical changes. In order to see how much 
justification there is for this idea I tried to discover whether 
lack of oxygen or an increase in the concentration of sea- 
water affects the embryo differently in different stages of its 
development.’ I used for these experiments the eggs of a 
marine fish (Fundulus). The eggs of this fish complete their 
development in about two weeks (at the proper temperature). 
We may discriminate three stages in the development of this 
fish. The first consists solely of processes of cell-division 
and the expansion of the blastoderm. This stage lasts about 
twenty-four hours. It is followed by the formation and 
beginning differentiation of the embryo during the second 
1 Part I, p. 309, 
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