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that "life is the continuous adjustment between internal relations and external relations." This, like Haeckel's statement that heredity is memory, is not very clear without explanation, but its meaning may perhaps be brought out by an illustration.
If I kick a stone I produce in it certain changes, such as motion, heat, etc.; these changes being directly produced by the kick are simply manifestations of the energy transferred from my foot to the stone. If, instead of a stone, I kick a dog, I produce a similar set of changes, and something more. The experience of the dog and of his ancestors has taught him that such violent attacks are always associated with a disposition to commit still further violence, so, when the dog feels the blow he immediately performs actions which have as their object, escape from or avoidance of the danger which he has not yet experienced, but which he knows to be imminent. These actions are not the effect of the kick, for the energy expended may be hundreds of times greater. . Their character is determined, not by any change in the dog, but by the character, the disposition, which he has inherited; and whether he retaliates by an attack on his own part, puts his tail between his legs and runs, or crouches at my feet, his actions are the effect, not of the kick, but of past experience as to the best means of escaping further injury. There is a relation, external to the dog, between the kick and a disposition to injure the dog, and there is within the dog a relation between the sensation of injury and the actions which experience has shown to be the proper ones for escaping further injury.
That which distinguishes the dog from the stone is the power to adjust these internal relations to the external relations, to conform his conduct to the laws of the world around him. The dog, as a living thing, differs from all inorganic bodies, in his power to make this adjustment: so long as he retains this power he lives; his life is a "continuous adjustment between internal rela tions and external relations." It is plain that this power depends upon experience, but experience depends I upon "memory." So we may state, with truth, that in a certain sense, life is memory; and as the power to reproduce its like is characteristic of all living things, we see that there is in Haeckel's statement a profound truth.
We know memory, however, only in connection with organization, and if it is true that heredity, the power of an organism to reproduce its like, is simply the memory, by the ovum, of the experience of its ancestors, we must believe that there exists in the ovum an • organization of some kind to correspond to each of these past experiences.
We are therefore driven by the hypothesis of perigenesis back from the hypothesis of epigenesis to some form of the old evolution hypothesis, for we cannot conceive that complicated experiences should exist without complicated structure.
We are thus compelled to conclude that, while it undoubtedly expresses a great truth, Haeckel's hypothesis of perigenesis is not a satisfactory and final explanation of the phenomena of reproduction. A satisfactory theory of heredity must explain what it is, in the structure and organization of the ovum, which determines that each ovum should produce its proper organism.
To state that this organization can be expressed in terms of memory, is simply to state the familiar truth that matter and force are different aspects of the same thing; that all problems of matter may be put into the terms of force. The statement does not help us at all to picture to ourselves the essential hidden structure of the egg, the organization upon which its wonderful properties depend.
Jager has recently brought forward an hypothesis which seems at first sight to be a satisfactory epigenesis hypothesis, but examination shows that this too, like Haeckel's perigenesis hypothesis, must be turned into an evolution hypothesis before it can be accepted.
The following extract from his paper ("Zur Pangenesis," von Prof. Dr. C. Jager. Kosmos iv. 376. 1879) gives, I believe, a fair statement of his views.
"Each organ and tissue of an animal or plant contains, in the molecules of its albumen at least, a specific flavor-and-odor-substance (Duft-und-Wurzestoff) which we can easily recognize by our chemical sense, for each organ of an animal has its distinctive flavor. Whenever a full-grown animal experiences hunger, decomposition of albumen takes place in all its organs and tissues, so that their various flavor-and-odor-substances, that is their soul-substance (Sezenstoffe), become free, and penetrate to all parts of the body.
"Now, if there exists in any part of the body protoplasm with the power to attract this substance, this protoplasm acquires in this way its vires formativce.
"I have already referred with emphasis to the embryological fact that the formation of the reproductive elements takes place at a very early stage in the embryonic life of an animal, and I have designated this as the reservation of germinal protoplasm. As soon as the embryonal cells of the developing animal have become specialized into ontogenitic and phylogenetic cells, the following will occur. Whenever any decomposition of albumen occurs in the developing organism, from himger'or any other cause, the ontogenetic cell-material whioh builds up the organism will set free soul-stuff.
"By the law of gaseous diffusion this will not only escape from the body as an excretion, but it will also penetrate to the germinal or phylogenetic protoplasm. This process I shall now term soul-reception (Seelenfangerei) in the following sense. The chemical substance which forms the greater part of the ova and male cells has lately been called nuclein, since it shows the closest resemblance to the cell-nucleus. The yolk-substance is now regarded, not as vitellin, but egg-nuclein, and the substance of the male cell not spermatin but sperm-nuclein. We also know that nuclein consists of albumin, and phosphoric lecithin.
"The question then is the origin of the nuclein in the egg, and the male cell, and this may be answered as follows:
"The reproductive organs do not receive albumen from the body of the mother, since according to the law of Traube, the molecules of a substance which forms a membrane cannot, on account of their size, pass through the pores of that membrane. The germ-cell is an albuminous membrane, and hence it will not allow the passage of albumin molecules.
"It simply contains the albumin-nucleus, which remains after the decomposition of the soul-substance, and this is a peptone-like substance which, having lost its soul-substance, has a smaller molecule. It is therefore unspecialized, or deprived of its soul (entspesificirt, entscelt), and the process of assimilation in the germ may be termed soul-restoration (Wiederbeseelung). The necessary soul-substance is supplied by the decomposition of albumen in the ontogenetic cell-material.
"Thus, for example (p. 380), it is known that the reproductive organs of a caterpillar are already formed before it leaves the egg. During its life in the egg, and as a caterpillar, caterpillar-nuclein is formed in its germinal cell-material. During the pupa stage pupa-nuclein is stored up in its reproductive elements, and finally, when it becomes a butterfly, butterfly-nuclein is stored up. The ripe egg and the ripe male cell therefore contain nuclein of three kinds, caterpillar-nuclein, pupannclein, and butterfly-nuclein."
It will be seen that Jager's hypothesis is, in a certain sense midway between evolution and epigenesis. He holds that at first both the ovum and the male-cell are unspecialized (entseelt); that they exist in the very young embryo as embryonic ova or spermatozoa, and that, as the embryo grows up, the reproductive cells gradually become specialized by the assimilation of soulstuff, which is thrown off by the decomposition <f albumen in various parts of the body of the grow? ig organism, and penetrating to the embryonic ova I ad spermatozoa is assimilated by them, so that when ohe animal becomes sexually mature, the cells of its r4 iroductive organs contain all the "soul-stuff" necessary to produce a new organism like the parent.
The statement which I have given is a free translation of Jager's outline of his theory, and I think it may be regarded as a fair exposition of his views.
A fatal objection to his hypothesis is found in the fnct that where a parent gives birth to young before it has reached full maturity and before it has acquired all the characteristics of the species, the young nevertheless inherit these characteristics. The young which are born by a Cycedomia larva inherit all the characteristics of the full-grown adult insect, and a bull may transmit to female children the good milking qualities of his