*» SPECIES." 1 1 5 



to show that the whole of the phenomena of Ontogeny- 

 forms a connected chain of evidence in favour of the truth 

 of the Theory of Descent, and that they can be explained 

 only by Phylogeny. With the aid of this close causal 

 connection between Ontogeny and Phylogeny, and by 

 constantly appealing to our fundamental law of Biogeny, 

 we shall be gradually able to prove from the facts of On- 

 togeny that Man is descended from the lower animals. 



In conclusion, it must be mentioned that very recently 

 the important theoretical question as to the nature and idea 

 of " kind," or " species," which is the point on which really 

 hang all the disputes about the Theory of Descent, has been 

 definitely settled. For more than a century this question 

 was discussed from the most varied points of view, without 

 resulting in a satisfactory settlement. During that time 

 thousands of zoologists and botanists have occupied them- 

 selves in systematically distinguishing and describing 

 species, without, however, any clear idea of the meaning 

 of " species." Many hundred thousand vegetable and 

 animal forms were set up and marked as good species, 

 though even those who declared them such were unable to 

 justify the proceeding, or to give logical reasons for thus 

 distinguishing them. Endless disputes arose among the 

 "pure systematizers," on the empty question, whether the 

 form called a species was " a good or a bad species, a species 

 or a variety, a sub-species or a group," without the question 

 being even put as to what these terms really contained and 

 comprised. If they had earnestly endeavoured to gain a 

 clear conception of the terms, they would long ago hav^ 

 perceived that they have no absolute meaning, but are 

 merely stages in the classification, or systematic categories, 

 and of relative importance only. 



