CREATION BY EVOLUTION
Inasmuch as many phenomena of development are mere adaptations to the conditions of embryonic or larval life and could never have been present in adult animals, Haeckel separated such characters, which he called “cænogenetic,” from the truly ancestral ones, which he called “palingenetic.” Unfortunately there was no certain method of always distinuishing these two types of embryonic characters, but in spite of this difficulty embryology was supposed to afford a short and easy method of determining the ancestral history of every group. Since every animal in its development from the egg to the adult condition was believed to climb its own ancestral tree, one can imagine the feverish zeal with which the study of embryology was pursued. Here was a method which promised to reveal more important secrets of the past than would the unearthing of all the buried monuments of antiquity — in fact nothing less than a complete genealogical tree of all the diversified forms of life which inhabit the earth. It promised to reveal not only the animal ancestry of man and the line of his descent but also the method of origin of his mental, social, and ethical faculties.
Unfortunately there was no certain criterion by which the palingenetic or ancestral features of development could be distinguished from the cænogenetic or recently acquired ones, and what one embryologist regarded as ancestral another might consider a recent addition. Furthermore, when there were no living or fossil animals resembling certain embryological forms the fancy was given free rein to invent hypothetical ancestors corresponding to such forms.
As a result of such speculations multitudes of phylogenetic trees sprang up in the thin soil of embryological fact and developed a capacity of branching and producing hypothetical ancestors which was in inverse proportion to their hold on solid ground. For a time embryology was studied chiefly
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