1895- PALAEONTOLOGY AND BIOGENETIC LAW. 311 



larger categories in botany and zoology are almost exclusively based 

 on the investigation of forms that still exist ; and it is only in those 

 divisions where the fossil forms surpass the recent ones, in number or 

 in variety of organisation, that they, too, have been taken at all into 

 account. As a rule it has been thought good enough to wedge in the 

 extinct Orders or Families between the groups erected by the botanists 

 and zoologists. Thus the foundations of the system remain intact. 

 It is only recently that attempts have been made to reconstruct 

 individual divisions of the zoological system, to a certain extent from 

 below, on a palaeontological basis. Thus, Scudder has established a 

 Sub-Class, Palaeodictyoptera, for all palaeozoic insects, because they 

 possess a series of common, indifferent characters, and show as much 

 morphological correspondence one with another as they do with the 

 later Orthoptera, Neuroptera, and Hemiptera, whose predecessors 

 can already be clearly recognised among the palaeozoic forms, although 

 they have not yet attained the complete differentiation of their later 

 descendants. Could we resurrect the numerous genera of the Puerco 

 Beds and place them among our fauna of to-day, we should doubtless 

 arrange them in one common Order, more or less corresponding to 

 the marsupials ; for, like the marsupials, they possess characters 

 that, at all events, point in the direction of Orders more clearly 

 differentiated later on, in which Orders we are at present accustomed 

 to enrol them. 



If the zoological and botanical systems were now to be created 

 for the first time, they would in many respects probably assume a 

 different appearance. They would have to represent clearly the 

 natural relationship and the derivation of the organisms. The 

 geologically oldest representatives of any of the larger assemblages, 

 which are as a rule also the most generalised and most primitive, 

 would have to be united under a special name, and would be regarded 

 as the common root of the Orders, Families, Genera, etc., proceeding 

 from them. But it is only in a few cases that palaeontology could 

 furnish the materials required for a reform of this kind. As a rule, 

 and especially among the invertebrates, the primitive generalised 

 types are missing, and we should be obliged to begin with those 

 branches and twigs from our stems which are already more clearly 

 differentiated, and of which the majority stretch down as far as the 

 creation of our own day. Here again, then, we should be led to 

 ground our classifications on those organisms of which we were in a 

 position to investigate not merely certain fossilisable elements, but 

 the whole anatomy, physiology, and embryology. 



The function of classification, however, is not only to arrange 

 organised beings according to their relationship, but also to facilitate 

 our survey of life's infinite variety of form. It was to this intent that 

 the older systematists constructed their various categories. They it 

 is that have historic rights ; and just as little as we geologists are 

 inclined, without urgent need, to alter the historic conceptions and 



