EFFECT OF IONS UPON TISSUE 565 



II. ON THE DIFFERENT EFFECTS OF IONS UPON UNDIFFER- 

 ENTIATED EMBRYONIC 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. 1 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 



i Part I, p. 309. 



