312 NATURAL SCIENCE. May, 1895. 



the divisions that have been handed down to us, just so little is it 

 advisable to be incessantly remodelling the systems of botany and 

 zoology. The doctrine of descent has, of course, violently shaken the 

 solid framework ,of the older classification. The ideas — variety, 

 mutation, species, genus, family, order, etc. — have become indefinite 

 and unstable; the boundaries between the systematic groups are con- 

 stantly being displaced, and bonds are burst that were once tightly 

 bound. An important part is played to-day by subjective opinions, 

 and when I think of the anxiety with which we elders — we who 

 received our scientific education before the Darwinian era — proceeded 

 to found a new species or genus, and compare it with the light- 

 hearted manner in which to-day species, genera, families, and orders 

 are set up and again put down, I am herein most forcibly impressed 

 by the difference between then and now. The domination of the 

 Linnaean and Cuvierian principles threatened systematic biology with 

 soulless paralysis : the unbridled subjectivity of recent times may 

 easily lead to anarchy. When, after investigating a certain number 

 of forms, every author feels called upon to reform the classification, 

 and where possible to introduce a new terminology, then arises the 

 danger that we shall lose our comprehensive survey of the richly 

 varied organic world, and that we shall use a language intelligible 

 only to the most narrow specialists and repellent to every layman. 



With this warning let me conclude. The Theory of Descent 

 has penetrated the descriptive branches of natural science with new 

 ideas, and set before them a nobler goal ; but we should never forget 

 that it remains only a theory, and one that has to be proved. I have 

 tried to make plain how greatly it is indebted for its establishment to 

 palaeontological research ; only I dare not conceal how many gaps 

 are constantly brought to light in the very process of our argument. 

 Science strives in the first place for truth. And the more clearly we 

 keep ourselves conscious of the insecurity of the foundation on which 

 our scientific theories rest, the more actively shall we bestir ourselves 

 to strengthen it by new observations and new facts. 



Karl v. Zittel. 



