Page:Popular Science Monthly Volume 67.djvu/250

244 quicker than light, but that is all, and the one who unravels the mystery will deserve to rank with the greatest of discoverers.

In like degree are we ignorant of electrical and magnetic phenomena which depend upon the ether. When the ether is understood we shall be able to understand in a mechanical sense how moving a magnet disturbs every other magnet wherever it may be, why chemical compounds are possible, why crystals assume geometric forms, and why cellular structure in plants and animals can embody what we call life. To discover the nature and mode of operation of this ether is the work of the twentieth century, and we may be sure that he who accomplishes this will deserve to rank with the highest; indeed it may fairly be said that in importance it is not secondary to anything known, for it is apparently concerned in all phenomena from atoms to masses as big as the sun.

The biologists have great problems on hand for solution. The nineteenth century work made it clear that all the forms of vegetable and animal life of to-day are the product of slow changes in form and functions of living things reaching back millions of years. The successions of some forms were well worked out and the principle established. We call it evolution and everybody nearly believes that this represents the truth in the matter, but how these changes occur and what necessitates them remain as mysterious as ever. Darwin spoke of natural selection. There were all sorts of variations in progeny, and the ones best fitted to the environments survived, but he gave no reason why there should be variations, and this is the great question to-day. Many are at work to discover this, and some who have worked in this line have stumbled upon some very unsuspected facts. There has been assumed that like would produce like, and that heredity could and would account for abnormal structures when parents for any reason through new environment had acquired new habits or new structures of any kind. Now it has been shown that such changes of structure or of habit seldom if ever appear in the progeny. For instance, no matter how many generations of mice have their tails cut off each new mouse has the same old length of tail. Each lamb has as many tail vertebrae as did those of hundreds of years ago, though all lambs have their tails cut off when young. Such acquired character is not inherited. Nature pays no attention to any changes save such as she herself initiates, and the conditions she herself adopts remain to be found out. Sometimes she makes monsters and sometimes geniuses, but never by external environment, always de novo. This throws overboard the principle good and thoughtful men have so long cherished, that the good habits of one generation would be a hereditary possession of the next. The conditions for heredity are now a most absorbing study among some of the foremost biologists. It is suggestive that at this late day such a reversal of opinion on this