136 MODERN IDEAS OF EVOLUTION 



cell is the early stage of all animals alike, we natu 

 rally ask, Is it meant that all these cells are really 

 similar, or is it only that they appear similar to us, 

 and may actually be as profoundly unlike as the 

 animals which they are destined to produce ? To 

 make this question more plain, let us take the case as 

 formally stated : From the weighty fact that the egg 

 j of the human being, like the egg of all other animals, 

 !is a simple cell, it may be quite certainly inferred 

 that a one-celled parent form once existed, from 

 .which all the many-celled animals, man included, 

 Ideveloped. 



Now let us suppose that we have under our 

 microscope a one-celled animalcule quite as simple in 

 structure as our supposed ancestor. Along with this 

 we may have on the same slide another cell which is 

 the embryo of a worm, and a third which is the em 

 bryo of a man. All these, according to the hypothe 

 sis, are similar in appearance, so that we can by no 

 means guess which is destined to continue always an 

 animalcule, or which will become a worm or may 

 develop into a poet or a philosopher. Is it meant that 

 the things are actually alike, or only apparently so ? 

 If they are really alike, then their destinies must 

 depend on external circumstances. Put either of 

 them into a pond, and it will remain a monad. Put 

 either of them into the ovary of a complex animal 

 and it will develop into the likeness of that animal. 

 But such similarity is altogether improbable, and it 



