322 THE POPULAR SCIENCE MONTHLY, 



Either organisms were evolved in a natural way, or they were created 

 in a supernatural way, independently of one another, Haeckel, then, 

 considers the evolution theory, first, as a universal cosmic idea, which 

 assumes one causal law for all natural phenomena — the theory of descent, 

 according to which all animals and plants are derived from simple pri- 

 mordial organisms ; and, second, as the theory of natural selection (Dar- 

 winism in the strict sense), according to which the transformation of 

 organisms has for its essential condition natural selection in the strug- 

 gle for existence. And, by-the-way, we here find in Haeckel for the 

 first time, if we are not mistaken, the admission that " the essence of 

 the theory of descent is not affected, whether we postulate one or 

 whether we postulate many common ancestral forms "(monophyletic 

 hypothesis, polyphyletic hypothesis). It used not to be so, and who- 

 ever did not believe in the primordial mammal, the primordial amniote, 

 the primordial fish, etc., was a lost man. In this admission we see the 

 signs of a reaction from the monophj^letic genealogies, which now fill 

 whole volumes. Haeckel then tries to prove that Virchow is a believer 

 in the creation theory, although he nowhere says as much openly. Vir- 

 chow's expression, which Haeckel quotes, that " the scheme of organiza- 

 tion within the species is immutable — like will beget like," is suscep- 

 tible of more than one interpretation. 



In the second chapter, entitled " Sure Proofs of the Theory of De- 

 scent," Haeckel rejects experiment as the highest means of proof, 

 which Virchow requires ; at the same time he asks : " What is there to 

 be proved by experiments ? What can experiment prove in this case ? " 

 But I must confess that I am not at all of his opinion. Haeckel is right 

 in maintaining that the artificial breeding of our domestic animals, such 

 as the horse, the pigeon, and the dog, and the culture of our garden- 

 plants and culinary vegetables sufficiently demonstrate the mutability 

 of species ; that the forms purposely developed by us differ from one 

 another far more than wild species do ; that the evidence against the 

 evolution theory, which was intended to be deduced from hybridiza- 

 tion, is only empty talk, without sense, because several species do pro- 

 duce fruitful hybrids : but that the limits of experiment are here reached 

 we can in no wise admit. Experiments like those made by Madame von 

 Chauvin with salamanders can be repeated, not only with the lower 

 vertebrates but also with the invertebrata, and must surely lead to very 

 important results. I believe I can predict that the activity of working 

 naturalists, as soon as the present rather artificial methods of harden- 

 ing and dissection of organs and of whole animals, which reign now 

 almost exclusively, shall have exhausted themselves, will be devoted 

 to such experiments as have for their aim to prove that transforma- 

 tions, such as we see in Xature, can be produced at pleasure. To make 

 this point clear, I will mention the eyeless cave-animals and parasites. 

 To any one, however little familiar with the history of the evolution and 

 the relations of these animals to others, they furnish a complete demon- 



