ON CARYOKINESIS. 1 69 



fish and that of a jelly-fish ; raise them under exactly 

 the same conditions. Both will undergo division and 

 subdivision, but the process will end in the production 

 of two entirely different organisms. The difference in 

 result cannot, therefore, be attributed to difference of 

 conditions under which they develop, but to something 

 inherent in the ova themselves. In other words, the 

 egg-cell of a jelly-fish must have had from the begin- 

 ning the potentiality of becoming a jelly-fish and nothing 

 else ; and similarly, the starfish ovum must have been 

 a potential starfish from the beginning. To imagine, 

 therefore, that all protoplasm is identical, because no 

 difference is recognizable by any means at our disposal, 

 must be an error. Deep within the two particles of 

 protoplasm which give rise to two different organisms, 

 there must be a corresponding difference which lies at 

 the bottom of all differences. In short, the eggs of two 

 different animals must be supposed to differ in their 

 elementary constitution, as much as their adult organ- 

 isms differ in anatomical structure. " From general 

 scientific principles," says Professor Sachs, "we must 

 assume that for each visible external difference of organ, 

 there is a corresponding difference in its material sub- 

 stance, exactly as we regard the form of a crystal as an 

 expression of the material properties of the crystallizing 

 substance." And again, says the distinguished German 

 botanist, '' Even the different shapes of the two sexual 

 cells — of an antherozoid or a pollen grain compared 

 with the oosphere — indicate plainly, that both are con- 

 stituted differently as to material, since the external 

 form as well as the internal structure of any body is the 

 necessary expression of its material constitution. Dif- 



