Let him then proceed to think of as many definite characteristics of his own as he possibly can, and then enter these characteristics in the column which he deems appropriate. It will be found that with the great majority of characteristics no difficulty will be presented, and it will be quite impossible to think of anything which is a physical part of himself, which cannot be placed in one or other of these three categories. Even though there may be a little difficulty as to which column should claim the entry, it will be found that this is due rather to indecision on the part of the reader than to anything else. It is not because he can imagine any other origin for the trait which is for the moment puzzling, but simply because he may be uncertain as to whether it is an inborn character, or one due to the subsequent action of circumstances. Thus he will have no difficulty in placing in the first column such characteristics as the possession of one nose, two eyes, the colour of his eyes, perhaps the shape of his nose, and so forth, these all being germinal inherited characters. Equally simple is it to see that in the second column must be placed such parts of his individuality as speech, writing, the size of his muscles at the moment, and so forth. These obviously have resulted from the action of circumstances on inborn capacities. No embryo can speak or write, though it has within it the inherited capacity to enable it to learn such things. Finally he may find it difficult to think of anything to place under the heading of “Variations”; but, on the other hand, should he happen to be a genius in music or mathematics, or the possessor of six toes or a black mole on his arm, these will indicate to him at once that they are of the nature of “Variations.” (It must be remembered, however, that they may be transmitted to successive generations, in which case they become germinal characters.)
In a similar way if the reader desires to follow out this analysis of the characters which make an embryo, and which, therefore, afterwards comprise the possibilities of an individual from the point of view of the stimuli under which they are developed, he may easily do so. Another sheet of paper similarly divided into three columns with the headings “Nutrition, Use, and Injury,” will enable him to see how his individual characteristics have attained their present development as the result of one or other of these stimuli acting upon the germinal or inherited tendencies. Without going into detail in this matter one may simply note that under the heading of “Injury” will come all those parts of himself of which he has become possessed as the result of disease or accident, whether this be physical, mental, or moral.
Now we have completed what was necessary to arrive at our conclusion of what it is that goes to the making of an embryo, and therefore of a human being—a personality. The conclusion is that every characteristic which it is possible for an individual under any circumstances whatsoever to possess is traceable ultimately to the action which takes place between his inherited tendencies and his natural environment. This environment, whether it be physical, mental, moral, ethical, spiritual, or whatever other can be imagined, can only produce the whole individual by means of acting upon what is already present. To that material nothing can be added except in the environment; from that material nothing can be taken away; the most that can be done in this direction is to hinder its growth by suitable procedures. Hence the truth of the phrase that “education is nothing more than the giving or withholding of opportunity.” Hence it is so entirely true that it is impossible to make a silk purse out of a sow's ear, or to gather grapes from thorns. The importance of thoroughly realising these simple facts of embryology should at this stage be obvious. They constitute possibly the most important lesson which is demanding attention at the hands of modern teachers, parents, and sociologists.
One further word before we leave this part of our subject. It is obvious that of our total characteristics some are acquired and some are inherited, and the question then arises, How much is inherited in an embryo or individual, and therefore unavoidable, and how much acquired? It would be beyond the scope of our subject in this place to enter into detail in this matter, but it would not be right to pass the question by without pointing out that a careful analysis of individual characteristics will show that under the heading of “Inherited” will be found principally the physical traits. When the reader comes to estimate his mental and moral characteristics, a very few moments' careful thought will prove most conclusively to him that these must be entered up under the heading of “Acquired.” If it were not so progress in those directions would be practically hopeless. But plain as is this truth, it is one which is far from being realised by many well-educated people.
CHAPTER V
FERTILISATION AND EARLY DEVELOPMENT
We may now turn our attention to the consideration of some of the phenomena connected with the early processes in the development of the embryo. We may assume that the eggs and sperms have reached such a stage in their life history that they are now mature. All that is necessary in order that the development of an embryo should result is that union of the two elements should take place. Many complicated changes have occurred in the constitution of these eggs and sperms before this stage is reached, but into these we need not enter. It will suffice for our purpose to assume that they are now mature. Then as the result of a natural instinct which suggests certain thoughts and emotions to the male and female animals, which in turn are followed by certain definite acts, the sperm-cell from the male and the egg or ovum-cell from the female are brought into contact. This contact takes place in such circumstances that the united elements are able to be protected and nourished and so, fertilisation having thus occurred, development begins.
The characters of these two wonderful cells, which by their union ultimately cause the production of an embryo, are briefly as follows. The element from the male, the sperm that is, is an extremely minute cell which is only about 1⁄300 of an inch in length. As seen under a high power of the microscope it is composed of two portions which are spoken of as a head and the tail. The former is a flat, oval part, and behind this is the rounded body ending in the long tail which is some four-fifths of the total length. This long tapering tail gives to the sperm its power of movement, for it is supposed that as the result of the rotating or lashing movements of this tail the cell is propelled. Indeed its rate of motion has been actually studied, and estimated to be at about one-eighth of an inch per minute.