Without question, de Vries had a real basis for his theory. Mutations do take place among both wild and domestic creatures; thus among the dandelions there constantly appear special types which breed true and are, as Castle has called them, “little species within the dandelion species.” Similar mutations are well known in peas, beans, evening primroses, and such domestic animals as the sheep. Clearly, therefore, species do arise as de Vries stated; the question is, is this the only way in which they arise? This problem was raised little more than twenty years ago--a period far too short to allow for the settling of a question that is merely another statement of the problem that has puzzled scientists and philosophers for more than twenty centuries. There is, however, excellent reason for believing that the conceptions of both de Vries and Darwin are true; that neither of them excludes the other from operation. Thus in the famous chalk formation of England there may be found an evolutionary chain of sea urchins which, according to the general consensus of opinion, represent true Darwinian evolution. As N. C. Macnamara says, “They are first found in their shelled, sparsely ornamented forms, from which spring, as we ascend the zone, all the other species of the genus. The progression is unbroken and minute in the last degree. We can connect together into continuous series each minute variation and each species of graduation of structure so insensible that not a link in the chain of evidence is wanting.” On the other hand, the writer has recently completed a microscopic study of a group of ancient lamp-shells--animals which looked somewhat like molluscs, but which were very different internally--with altogether different results. The particular changes involved were minor matters of surface markings, which could have had no conceivable importance to the animals. Selection, therefore, may be virtually ruled out; indeed, many of the different forms lived close together, with apparently equal success. But in the small markings on the shells there appear, as one follows the series from bottom to top, very decided changes, and those changes are, in some cases, abrupt and complete. In others the variations are very small--indeed they could be distinguished only with the microscope--but so far as could be told, were distinct. This, therefore, points to a course of evolution that was clearly a matter of mutation, without any apparent governing by the process of natural selection.