1896. ZOOLOGY AFTER DARWIN. 197 



satisfactory extension of the doctrine of the homology of the germ- 

 membranes, propounded frequently with so much assurance, is not to 

 be thought of. 



Doubly valuable, therefore, seemed the morphological facts 

 gleaned from another field of phylogenetic knowledge, namely, the 

 history of fossil forms. Originally an aid to geology, it developed, in 

 the period we are reviewing, into an independent branch of learning, 

 and has borne richer fruit in proportion as it recognised the necessity 

 of going hand in hand with the history of recent forms. ^ Zoology and 

 palffiozoology have both the one chief aim, to illustrate the history of 

 animal life on our earth; and a collection answering to modern ideas, 

 which would strive to show an exact picture of present genealogical 

 materials and facts, would have to retain, arranged alongside of recent 

 forms, the fossil remains of extinct species. The service which 

 palaeontology has done with regard to synthetic types and tran- 

 sition-forms, as well as to classical evolutioa-ssi'ies, is the more 

 important for the completion of the animal pedigree, since the exact- 

 ness of description permitted by fossils, and the facilities they afford 

 us for verifying their actual relations, lend a certainty and trust- 

 worthiness to most palaeontological statements not possessed by the 

 morphology of recent forms. 



Darwin cautiously left untouched a number of questions not of 

 importance to his selection theory. In fact, it is immaterial to this 

 theory how one may imagine the primary origin of the simplest forms 

 of life, so long as the existence of these forms is proved. In the same 

 way the theories of descent and of selection were unaffected by the 

 circumstance that at the time of their conception one could not 

 picture the concrete foundations of heredity or the primary causes of 

 variability. The existence of these phenomena sufficed as the founda- 

 tions of the theory. But when, chiefly by German naturahsts and 

 philosophers, the amplification of the theory of descent had given rise 

 to a new philosophy of the universe, these weighty questions had to be 

 discussed. Yet, as ^regards the first of them, the primary creation of 

 the organism, we have progressed no further than a theoretical 

 formulation. 



Since there are no chemical elements peculiar to vitality ("life 

 materials"), and since a special " life force " could not be proved, our 

 only alternative was to accept the idea of a " first origin " of the 

 simplest organisms from inorganic elements with the co-operation of the 

 forces active in such inorganic elements. ^Moreover, since the material 



1 Into this new path palreontology was led chiefly by K. von Zittel. By teach- 

 ing and research, as well as by the inimitable arrangement of the palaeontological 

 collection at Munich, von Zittel has striven to penetrate deep into palaeontology and 

 zoology, and his splendid " Grundziige der Pala?ontologie " is the result. C/. also 

 von Zittel's " Die Palaeontologie und das biogenetische Grundgesetz," in Aula, a 

 weekly journal for the academic world, I. Jahrg., p. 3S5, Munich, 1S95 [trans- 

 lated in Nato'ral Science for May, 1S95], and also F. v. Wagner's Referat ira 

 Biologischen Centralblatt, XV. Bd., p. 840, Leipzig, 1S95. 



