is certainly no difficulty in believing that these instincts have had a male origin.

The remarkable instinct which leads some species of cuckoo and crow blackbirds to lay their eggs in the nests of other species, must have originated in females, and a collection of all the cases which must be explained in the same way would make a formidable list, but the fact would still remain true, that among animals with separate sexes, male modifications are very much more frequent than female modifications, and this is all that our theory requires.

CHAPTER X.

THE EVIDENCE FROM THE INTELLECTUAL DIFFERENCES BETWEEN MEN AND WOMEN.

(This chapter, which was published in the Popular Science Monthly for June and July, 1879, under the title, "The Condition of Women from a Zoological Point of View," is reprinted here, almost without change.)

ZOOLOGY is the scientific study of the past history of animal life, for the purpose of understanding its future history. Since man has, in part at least, conscious control of his own destiny, it is of vital importance to human welfare in the future that we should learn, by this comparative study of the past, what are the lines along which progress is to be expected, and what the conditions favorable to this progress, in order that we may use our exceptional powers in harmony with the order of nature.

The study of the growth of civilization shows that human advancement has been accompanied by slow but constant improvement in the condition of women, as compared with men, and that it may be very accurately measured by this standard. Judging from the past, we may be sure that one of the paths for the future progress of the race lies in this improvement, and the position of women must therefore be regarded as a most important social problem. If there is, as I shall try to show, a fundamental and constantly increasing difference between the sexes; if their needs are different, and

if their parts in the intellectual, moral, and social evolution of the race are, like their parts in the reproductive process, complemental, the clear recognition of this difference must form both the foundation and superstructure of all plans for the improvement of women.

If there is this fundamental difference in the sociological influence of the sexes, its origin must be sought in the physiological differences between them, although the subject is now very far removed from the province of ordinary physiology. While we fully recognize the insignificance of the merely animal differences between the sexes, as compared with their intellectual and moral influence, it is none the less true that the origin of the latter is to be found in the former; in the same manner -to use a humble illustration-that the origin of the self-denying, disinterested devotion of a dog to his master is to be found in that self-negation which is necessary in order that a herd of wolves may act in concert under a leader, for the general good.

In order to trace the origin and significance of the differences which attain to such complexity and importance in the human race, we must carry our retrospect back far beyond the beginning of civilization, and trace the growth and meaning of sex in the lower forms of life. In so doing I shall ask attention to several propositions which may not at first appear to have any bearing upon our subject, or any very close relation to each other. I shall then try to show what this relation is, and point out its bearing upon the education of women.

Every organism which is born from an egg or seed is a resultant of the two systems of laws or conditions which may be spoken of abstractly as the law of heredity and the law of variation, or, to use the old teleological terms, each organism is a mean between the principle of adhe

rence to type and the principle of adaptation to conditions.

That like produces like is universally but never absolutely true. The offspring resembles its parents in all fundamental characteristics. The human child, for instance, resembles its parents in the possession of all the characteristics which distinguish living things from those which are not alive, as well as those which distinguish animals from plants. The chemical, physical, and physiological changes which take place in its body and the histological structure of its tissues are like those of its parents, and its various organs are the same in form and function. All the characteristics which unite it with the other vertebrates, as a member of the subkingdom Vertebrata, are like those of its parents, and also those which place it in the class Mammalia, and in its proper order, family, genus, and species. It also shares with its parents the features or race characteristics of the particular tribe or race to which they belong. If they are Chinese, Indians, or negroes, the child belongs to the same race, and manifests all the slight, superficial peculiarities of form, constitution, and character by which that race is distinguished. Even the individual peculiarities of the parents, intellectual and moral as well as physical, are now known to be hereditary. Since this holds true of any other animal or plant, we must recognize the universality of the law of heredity, but we must not overlook the equally well-established fact that each organism is the resultant of this law and another, the law of variation. The child is like its parents, but not exactly like them. It is not even a compound of characteristics found in one or the other of them, but has individual peculiarities of its own; slight variations which may not have existed in either

parent, or in any more remote ancestor. The slight individual differences are so overshadowed by the much more conspicuous resemblances due to heredity-with which they compare about as the green buds at the tips of the twigs of a large tree compare with the hard wood of the trunk and branches, the growth of previous years -and they are so fluctuating and inconstant, that their importance may easily escape attention. Careful observation shows, however, that every characteristic may vary: those distinctive of the class or order as well as those which mark the species or variety. The variations may manifest themselves in the adult, or at any other period in the life of the individual. Even the eggs have individualities of their own, and among many groups of animals the eggs of the same parent, when placed under precisely similar conditions, may differ in the rate and manner of development. Although most of these individual differences are transient, and disappear within a few generations, there can now be no doubt that those which tend to bring the organism into more perfect harmony with its environment, and are therefore advantageous, may be established as hereditary features, through the action of the law of the survival of the fittest; and it is hardly possible to over-estimate the value of the evidence which paleontology and embryology now furnish to prove that all hereditary characteristics, even the most fundamental, were originally individual variations.

The series of hereditary structures and functions which makes up the life of an organism is constantly being extended by the addition of new features, which, at first mere individual variations, are gradually built into the hereditary life history. In this way newly acquired peculiarities are gradually pushed further and further from what may be called the growing end of the series,