found that at the 100th division degeneration began and increased to the 240th. At the 130th generation, sexed individuals appeared, which were about half the original volume. At the last fission the animals were only 1-60 of the original volume. At the 316th division he isolated one of the 510 individuals and found that it produced "nothing but abortions, incapable of reproducing, and which shortly died."1 This extinction Maupas calls senile degeneration, thus very questionably homologizing this series of separate cells, artificially prevented from normal conjugation, with a series of mutually dependent and connected cells such as may be found in any metazoan. A. M. Marshall2 appears to accept this homology, but nevertheless agrees with Weissmann in thinking that death is not an intrinsic necessity of life, but appears first in the higher protozoan in close reciprocal connection with conjugation and reproduction. Since we do not know, says he,3 "at what period or to what extent the somatic cells of a metazoan lose their power of conjugating," nor what occurs in vaccination or transfusion of blood, he suggests, as a matter of theory, the possibility of discovering some means of rejuvenescence for the somatic cells, a possibility which G. A. Stephens of Norway Lake, Me. ("Long Life"), in establishing a laboratory for the purpose, seems to be inclined to devote some effort towards realizing!

Other special hypotheses on the causes of death have not been particularly fruitful. Bütschli thinks that life is the result of a ferment which the protozoans and the germinative plasma have the power of manufacturing. When the ferment is exhausted, life ceases. According to Lendl every cell by the very fact of living accumulates in it substances, some useful, some not, which are nevertheless foreign to the pure germinative plasma. This material he calls ballast, and regards it as the cause of death. The reproductive cells keep themselves pure by loading this material on to other cells. He supposes that the protozoans divide so that one cell retains the ballast, while the other is free. A certain number of the protozoans are thus doomed to death. Delboeuf says that the precipitation of the substance of the organs towards the inorganic causes death. Dantec represents death with

J. Delbœuf, "Pourquoi mourons-nous ?"

1891.

Rev. Phil., Mar. and Apr.,

2" Biological Lectures and Addresses," chap. on Death, p. 283. 3 P. 287.

✦“Gedanken über Leben und Tod,” Zoöl. Anz., V, 64-67.

366

Hypothese über die Entstehung von Soma- und Propagationszellen." Jena, 1890.

Art. cit.

'Rev. Phil., Jan., Feb. and May, 1895.

the primitive forms as an alternative to evolution, or change into another species. This becomes necessary, both because material for assimilation becomes exhausted owing to the narrow confines of the globe, and formed products are left within the plastid. He thinks that it might be much more possible to develop a new species from a moner than to begin higher up the scale where the plastids or individual cells are already highly developed. Delage,1 observing the almost universal correlation of differentiation with loss of germinative power, looks upon differentiation as the cause of death. Minot2 insists upon the converse of this and regards the embryo as a special arrangement permitting the increase of undifferentiated cells, and consequently a higher organization. Spencer says that for both somatic and germinal cells it is a matter of environment which may permit or not the continuance of nutrition.

Of the general vital theories, all of which bear upon the question of death and senility, we shall be forced to confine ourselves to a brief mention of the ideas of Roux, which perhaps, because he has paid the greatest attention to ontogeny, apply more directly to the concrete facts, about to be discussed, of the last stage of human existence, where, with the ceasing of the deeply hereditary racial or reproductive life, the more purely individual or ontogenetic features are more sharply defined. Roux is described by Delage in contrast with the animists, evolutionists, and micromerists as an organicist, by which he means the acceptance of a moderate determination by heredity with the addition of "surrounding forces, always active, always necessary, not simply the condition of activity, but an essential element of the final product."4 Roux thus harmonizes the extremes of Weissmann and Goette, already referred to, by bringing to view the fact of an internal or physiological struggle for existence among the organs, the cells, and the protoplasmic molecules of the organism. "This unsimilarity of parts," says he,5 "makes it impossible to establish laws of heredity which shall govern details of function to the last cell or molecule,-as in any army the commander-in-chief does not give special orders beforehand affecting every private in the ranks. There must be a possibility of adaptation to surroundings, especially in details, which, too, are more

3"Der Kampf der Theile im Organismus," Leipsic, 1881.

4

Op. cit., p. 720.

"Der Kampf der Theile im Organismus,” p. 71.

easily changed than events on a larger scale." How is this freedom of organs and of adaptation obtained?

Roux believes that the principle that lies back of all development of tissues and organs is over-compensation of what is used, a quality which permits self-regulation, and is really a necessary precondition of life. Living matter, unlike inorganic matter, presents an external continuity in spite of the change of conditions. To effect this, assimilation must always be in excess (over-compensation), for if less than consumption the organism comes to an end of itself. If equal, conditions change, and nourishment will fail or injurious events will cause destruction. Continuance can only be assured when more is assimilated than is consumed. He illustrates this by the example of fire, which assimilates more than it uses, i. e., it always has energy left over to kindle new material. This would (like life) become eternal if it did not use up materials quicker than other processes can make them. In the same way organisms assimilate more than they consume, but they do not turn all they use to assimilation; energy remains over by which the process performs something. This workproduct controls the excessive assimilation which otherwise would come to an end by not having sufficient material to assimilate. He thus regards the more complex processes of life as essentially a radiation of assimilation, which, although not identical with combustion, is similar to it, the load which it carries favoring its continuity. This radiation, load, or work-product becomes directed, of course, by natural selection, to keep up a supply of food, primarily by moving the assimilating mass. Performance of function over and above assimilation is just as much a condition of continuous assimilation as assimilation itself is of performance. On the other hand there comes to be an inverse relationship between growth and production (within limits), and we have capacities which, although they use up material, do not in themselves increase assimilation. The course of development consists in properly directing this work-product.1

The proper growth of the higher centres favors permanence. Idiots age much earlier and die younger than normal people. Too rapid growth seems connected with this. Geoffroy St. Hiliare (Hist. des Nom., 17th ed., Vol. I, p 197) has given full particulars of a boy of six who was five feet high and broad in proportion. His growth was so rapid that it could almost be seen. He had a beard, looked like a man of thirty, and had every indication of perfect puberty. He had a full, deep bass voice, and his extraordinary strength fitted him for all country work. At five he could carry any distance three measures of rye weighing 84 lbs., and at six years and a few months he could easily carry on his shoulders bur

This so far represents merely a continuous productability of function in connection with assimilation. But a productability which is stored up and discharged by an outer stimulus of environment will be much more economical, and will give rise to what we find as reflex excitability. When this reflex work-product dominates, according to circumstances, function will sometimes be greater and sometimes less. If under these conditions assimilation keeps on continuously, there must sometimes be an overplus, sometimes a balance, and sometimes by excessive function death, and thus elimination. To avoid this last, it is necessary that assimilation should depend upon use or upon a stimulus which use calls forth. From the psychical side this stimulus is recognized as hunger.

This kind of process where stimulus is an indispensable factor, is more special and limited than the more general process of assimilation plus movement, etc., but has characteristics which favor it greatly in the struggle for existence. "Connected with the most complete self-regulation of functioning is the greatest saving of material, while those parts always according to their use are strengthened and grow, the unused degenerate and the material for their subsistence is saved. This kind of process unites the greatest economy with the highest functioning of the whole, but at the cost of the independence of the parts." Senescence becomes thus a result of differentiation, in which the parts exist merely on account of the function which they perform for the whole. The senescing organs wither up like state officials after pensioning, although they may linger on as pensioners for a long time, and may even descend in this condition from generation to generation, a fact which often allows of fresh starts in development. During the course of a life-time the organism moves from a more general, more easily impressible condition to one which is more perfectly mechanized. "Through a long period it becomes, through the continuous working of a given stimulus, more completely adapted to itself, and also more differentiated, and thereby more stable, so that an always increasing opposition is formed to the additional development of new forms and characteristics."2

dens weighing 150 lbs. But he did not become a giant, as every one expected. He soon got feeble, deformed, his intellectual faculties did not develop. He became idiotic and soon died. Bébé, the court fool of King Stanislas, had all the attributes of decrepitude at 23 years.

1"Der Kampf der Theile im Organismus," p. 224.

2 Op. cit., p. 201.

Dantec,1 while opposing himself to Roux in many points, really offers a simpler form of Roux's conception of overcompensation of used material. According to him function and assimilation are not to be separated at all. He evidently rejects the ordinary analogy of a machine capable of wearing out or running down (fatigue), and regards the activity of every cell or plastid as a chemical combination in which the substances which increase the growth of the plastid are added to the living matter. During the same reaction, however, there may be by-products formed, which, until their removal from the neighborhood, stand in the way of future reaction (fatigue, senility, etc.). Dantec also simplifies the question of death by emphasizing the fact that what dies is always the cell or plastid, or a number of them. The death of a many-celled individual is nothing additional or independent of this.

Longevity and Natural Selection. Whether senility or death is ultimately the most deeply rooted in the vital process, there seems to be no doubt that in the case of man as compared with the animals most closely related to him, the last of the old age period at least, has come in as a survival, which is correlated with, if it does not owe its existence in the struggle for existence to the greater development of the higher moral and sympathetic qualities of the race.2 Other reasons, however, have prepared the way, or assisted in this result. Among many of the lower animals a long life is frequently a necessity for the species, when it is associated with decreased fertility or lack of ability to raise offspring. Eagles, for example, live to about 60, but owing to the dangers to which the eggs and young are exposed from weasels, mice, etc., it takes about this time to successfully raise a pair. Many plants and animals, on the other hand, make up for their short lives by great fertility. This distinction, it is evident, is only of value when comparing species, and is of very little significance for the individual. With some animals, as with man, where the period for raising the young is long, it is found that life is normally increased to this extent beyond the actual sexual period. 4

But beyond the immediate value for the offspring, in man at least there is an added value in old age for the tribe and

1 Rev. Phil., Feb., Mar., 1896.

2Cf. G. M. Humphrey, M. D., "Old Age," 1889, p. 8. 'Weissmann, "The Duration of Life," p. 13.

With man the period of growth is variously put, and is actually different in different peoples and classes, the higher classes of the highest races not ceasing to grow physically till about 30. If the grand climacteric be placed at 50 (often earlier), this would give 80 years as the normal life-time, the latter 30 years of which is held in fee for the support and education of the young.