This discontinuity of development receives strong additional illustration from a survey of special subdivisions of ancient culture. Though the Palæolithic era certainly preceded the later Stone Age, archæologists have hitherto failed to show the steps by which the later could develop out of the earlier. This gap may, of course, be due merely to our lack of knowledge. Yet when we take subdivisions of the Palæolithic period, the same fact once more confronts us. There is no orderly progression from Solutrean to Magdalenian times. The highly developed flint technique of the former dwindles away in the latter and its place is taken by what seems a spontaneous generation of bone and ivory work, with a high development of realistic art. In view of the evidence, it seems perfect nonsense to say that early European civilization, by some law inherent in the very nature of culture, developed in the way indicated by archæological finds. Southern Scandinavia could not possibly have had a bronze age without alien influence. In this case, discontinuity was the result of cultural contact. It may be that the lack of definite direction observed throughout the Stone Age may in part be due to similar causes, the migrations and contact of different peoples, as Professor Sollas suggests. But it is important to note that discontinuity is a necessary feature of cultural progress. It does not matter whether we can determine the particular point in the series at which the significant trait was introduced. It does not matter whether, as I have suggested in the discussion of racial features, the underlying _causes_ of the phenomena proceed with perfect continuity. Somewhere in the observed cultural _effects_ there is the momentous innovation that leads to a definite break with the past. From a broad point of view, for example, it is immaterial whether the doctrine of evolution clings to the name of the younger or the elder Darwin, to Lamarck or St. Hilaire; the essential thing is that somehow the idea originated, and that when it had taken root it produced incalculable results in modern thought. If culture, even when uninfluenced by foreign contact, progresses by leaps and bounds, we should naturally like to ascertain the determinants of such ‘mutations.’ In this respect, the discontinuity of indigenous evolution differs somewhat from that connected with cultural development due to diffusion. It was absolutely impossible that Scandinavia should produce bronze in the absence of tin. But _a priori_ it is conceivable that an undisturbed culture might necessarily develop by what biologists call ‘orthogenetic evolution’, _i.e._, in a definite direction through definite stages. This is, indeed, what is commonly known as the classical scheme of cultural evolution, of which men like Morgan are the protagonists. Now, how do the observed facts square with this theoretical possibility?