342 THE HISTORY AND SCOPE OF ZOOLOGY IX 



distinguish characters which are of class value, others 

 which are only of ordinal value, and so on, so that the 

 classes of one sub-kingdom should on paper, and in 

 nature actually do, correspond in relative value to 

 those of another sub-kingdom, and the orders of any 

 one class similarly should be so taken as to be of equal 

 value with those of another class, and have been 

 actually so created. 



The whole position was changed by the acquies- 

 cence, which became universal, in the doctrine of 

 Darwin. That doctrine took some few years to pro- 

 duce its effect, but it became evident at once to those 

 who accepted Darwinism that the natural classification 

 of animals, after which collectors and anatomists, mor- 

 phologists, philosophers, and embryologists had been 

 so long striving, was nothing more nor less than a 

 genealogical tree, with breaks and gaps of various ex- 

 tent in its record. The facts of the relationships of 

 animals to one another, which had been treated as the 

 outcome of an inscrutable law by most zoologists and 

 glibly explained by the transcendental morphologists, 

 were amongst the most powerful arguments in support 

 of Darwin's theory, since they, together with all other 

 vital phenomena, received a sufficient explanation 

 through it. It is to be noted that, whilst the zoolo- 

 gical system took the form of a genealogical tree, with 

 main stem and numerous diverging branches, the 

 actual form of that tree, its limitation to a certain 

 number of branches corresponding to a limited number 

 of divergences in structure, came to be regarded as the 

 necessary consequence of the operation of the physico- 



