CHAPTER XIV 



KRXST IIAECKEL AND CARL (JKGKNUAUR 



AT the time when Darwin's work appeared there already 

 existed, as we have seen, a fully formed morphology with set 

 and definite principles. The aim of this pre-evolutionary 

 morphology had been to discover and work out in detail the 

 unity of plan underlying the diversity of forms, to disentangle 

 the constant in animal form and distinguish from it the 

 accessory and adaptive. The main principle upon which 

 this work was based was the principle of connections, so 

 clearly stated by Geoffroy. The principle of connections 

 served as a guide in the search for the archetype, and this 

 search was prosecuted in two directions first, by the com- 

 parison of adult structure ; and second, by the comparative 

 study of developing embryos. It \vas found that the 

 archetype was shown most clearly by the early embryo, and 

 this embryological archetype came to be preferred before the 

 archetype of comparative anatomy. It became apparent also 

 that the parts first formed (germ-layers) were of primary 

 importance for the establishing of homologies. 



While practically all morphologists were agreed as to the 

 main principles of their science, they yet showed, as regards 

 their general attitude to the problems of form, a fairly 

 definite division into two groups, of which one laid stress 

 upon the intimate relation existing between form and 

 function, while the other disregarded function completely, 

 and sought to build up a "pure" or abstract morphology. 

 In opposition to both groups, in opposition really to 

 morphology altogether, a movement had gained strength 

 which tended towards the analysis and disintegration of the 

 organism. This movement took its origin in the current 



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