Origin of the ter. Another necessary conclusion is this, that race characteristics imply direct personal relationship among those who exhibit them. The Englishmen of to-day are such because they are related by blood. They are the variously intermingled descendants of some few robust families of a thousand years ago, a hundred thousand of them at the most. "Saxon and Norman and Dane are we." From these familiesDane, Norman, and Saxon-the weak, the infertile, and the unfortunate are constantly undergoing elimination, leaving the strong and fecund to persist. The withered branches are only kept in existence through misplaced charity which continues the pauper; or through bad social conditions which propagate the criminal. Pauperism, criminality, and folly have their lineage, but it is not a long one; and wiser councils will make it shorter than it now is. This persistence of the strong shows itself in the prevalence of the leading qualities in the dominate strains. To these dominant ancestors every line of deviation will be found to lead, when we come to follow it, backward. In following the pedigree of an individual backward for a thousand years, we find that millions of duplications must occur in his ancestry. That is, thousands of persons would be reached from one to a thousand times each in the following up of different ancestral lines. The growth of colonial types comes from the narrowing of the range of crossing and from intermarriage with lines not English, which occurs most frequently outside of England. This is especially true in the United States. But in a few centuries these same conditions will unite to form a "Brother Jonathan" as definite in qualities and as "set in his ways" as his ancestor, the traditional “John Bull.” Race types and the survival of the existing. Race types thus arise from the "survival of the existing," its best results modified and preserved by the "survival of the fittest." Actual presence in a country of certain ancestral stocks is the first element. Their characters become workable, durable, and at last "ineradicable" by the survival of those in whom those characters are elements of life. An "unworkable" heredity destroys its possessor, and with him the line of possible descent. VI. THE PHYSICAL BASIS OF HEREDITY. BY FRANK MACE MCFARLAND. ALL living organisms, animals as well as plants, are built up of certain elementary parts or units termed cells. No matter how widely divergent The cell theory. in external appearance or habitat they may be, the elephant and the lily, the sponge and the palm, are each aggregations of structural units, fundamentally alike, and no form of animal or plant life is known to exist which does not conform to this general law. To the studies of Schleiden upon plants and of Schwann upon animals (1838-'39) we owe the foundation of the "cell theory," more precisely formulated by Max Schultze in 1861. Since the time of these pioneer studies upon the cell, investigation has been carried on by a constantly increasing number of students with methods and instruments steadily improved in their efficiency, and the accumulated results already throw a wealth of light upon some of the most abstruse problems of biology. Yet the most enthusiastic and sanguine of these workers will not assert that we have advanced further than the threshold of this domain in which are concealed the answers to the questions as to the ultimate structure of living matter and even to the very nature of life itself. The accumulating results of patient study have totally changed the earlier conceptions of the cell. Two and a quarter centuries ago, by the aid of the newly invented microscope, minute cavities were discovered in certain plant tissues, and from their resemblance to a honeycomb were termed "cells." This study of such substances as ordinary cork, in which the cells are dead and empty, easily led to the idea that the cell wall was the all-important feature, and it has not been until within the past forty years that this error has been set aside. The name "cell" itself is some the term "cell." The meaning of what misleading in that it implies, in the ordinary usage, a cavity with definite walls of considerable firmness, which is by no means always true. Great groups of cells have no solid walls whatever, but are soft and changeable in form, and the majority of cells have no cavities, but are masses of semifluid consistence. The appearance of empty cavities, or clear fluid-filled spaces, is a condition which comes about in plant cells late in life, and scarcely ever in animal ones. The unwearied study of biologists, aided by constantly improved instruments and methods of research, have shown that it is the contents of the cell which form the essential living substance. But, although the cell wall has lost the significance which it formerly was held to possess, the term cell has become firmly fixed by usage, and such terms as "Energide," as proposed by Sachs, though much more happily chosen, are very slow of adoption. The simplest forms of life of which we know anything are minute microscopic organisms found in both fresh and salt water and under the most varied conditions. Each one of these is composed of a single cell, and each one carries out in a general way the varied functions of movement, respiration, growth and multi Unicellular and multicellular organisms. plication, assimilation, secretion, excretion, irritability, etc., functions which, in multicellular organisms, are divided up among a vast number of the constituent cells. Thus while the onecelled amoeba has its muscular, nervous, and digestive systems united within the limits of a single microscopic mass of protoplasm, the higher animals have their various functions divided up among definite groups of thousands and millions of cells, each group carrying out some particular function. In response to this physiological division of labour among the cells has come about a corresponding modification in their structure, so that we find certain forms and types characteristic of the particular function which the respective cells carry out. The muscle cell, for example, is one whose special work is that of contraction. Within its substance has been developed a system of highly contractile fibrils, and the whole cell has assumed an elongated shape. For this one function of contractility have been sacrificed more or less completely the other properties of protoplasm, and thus it has become dependent upon its fellows which have assumed various other functions. The bone cell, the gland cell, the epithelial cell-all have equally complicated specializations of structure in other directions and, all united together into an organic community, are co-ordinated and directed in their various activities by the nerve cells. The essential parts of the cell. However diverse the form and function of the adult tissues may be, they all have the same fundamental structure, and they all have a common origin and descent from the fertilized egg cell. The essential parts of a cell consist of the cell body and the cell nucleus, which together make up the living substance. The body of the cell is made up principally of a granular, viscid, semi |