The Principles of Biology, Volume 1 (of 2)

12

This interpretation is said to be disproved by the fact that the carbo-hydrate contained in muscle amounts to only about 1.5 of the total solids. I do not see how this statement is to be reconciled with the statement cited three pages back from Professor Michael Foster, that the deposits of glycogen contained in the liver and in the muscles may be compared to the deposits in a central bank and branch banks.

13

Before leaving the topic let me remark that the doctrine of metabolism is at present in its inchoate stage, and that the prevailing conclusions should be held tentatively. As showing this need an anomalous fact may be named. It was long held that gelatine is of small value as food, and though it is now recognized as valuable because serving the same purposes as fats and carbo-hydrates, it is still held to be valueless for structural purposes (save for some inactive tissue); and this estimate agrees with the fact that it is a relatively stable nitrogenous compound, and therefore unfit for those functions performed by unstable nitrogenous compounds in the muscular and other tissues. But if this is true, it seems a necessary implication that such substances as hair, wool, feathers, and all dermal growths chemically akin to gelatine, and even more stable, ought to be equally innutritive or more innutritive. In that case, however, what are we to say of the larva of the clothes-moth, which subsists exclusively on one or other of these substances, and out of it forms all those unstable nitrogenous compounds needful for carrying on its life and developing its tissues? Or again, how are we to understand the nutrition of the book-worm, which, in the time-stained leaves through which it burrows, finds no proteid save that contained in the dried-up size, which is a form of gelatine; or, once more, in what form is the requisite amount of nitrogenous substance obtained by the coleopterous larva which eats holes in wood a century old?

14

This chapter and the following two chapters originally appeared in Part III of the original edition of the Principles of Psychology (1855): forming a preliminary which, though indispensable to the argument there developed, was somewhat parenthetical. Having now to deal with the general science of Biology before the more special one of Psychology, it becomes possible to transfer these chapters to their proper place.

15

See Westminster Review for April, 1852. – Art. IV. "A Theory of Population." See Appendix A.

16

This paragraph replaces a sentence that, in The Principles of Psychology, referred to a preceding chapter on "Method;" in which the mode of procedure here indicated was set forth as a mode to be systematically pursued in the choice of hypotheses. This chapter on Method is now included, along with other matter, in a volume entitled Various Fragments.

17

Speaking of "the general idea of life" M. Comte says: – "Cette idée suppose, en effet, non-seulement celle d'un être organisé de manière à comporter l'état vital, mais aussi celle, non moins indispensable, d'un certain ensemble d'influences extérieures propres à son accomplissement. Une telle harmonie entre l'être vivant et le milieu correspondant, caractérise evidemment la condition fondamentale de la vie." Commenting on de Blainville's definition of life, which he adopts, he says: – "Cette lumineuse définition ne me paraît laisser rien d'important à désirer, si ce n'est une indication plus directe et plus explicite de ces deux conditions fondamentales co-relatives, nécessairement inséparables de l'état vivant, un organisme déterminé et un milieu convenable." It is strange that M. Comte should have thus recognized the necessity of a harmony between an organism and its environment, as a condition essential to life, and should not have seen that the continuous maintenance of such inner actions as will counterbalance outer actions, constitutes life.

[When the original edition was published Dr. J. H. Bridges wrote to me saying that in the Politique Positive, Comte had developed his conception further. On p. 413, denying "le prétendu antagonisme des corps vivants envers leurs milieux inorganiques," he says "au lieu de ce conflit, on a reconnu bientôt que cette relation nécessaire constitue une condition fondamentale de la vie réelle, dont la notion systématique consiste dans une intime conciliation permanente entre la spontanéité intérieure et la fatalité extérieure." Still, this "conciliation permanente" seems to be a "condition" to life; not that varying adjustment of changes which life consists in maintaining. In presence of an ambiguity, the interpretation which agrees with his previous statement must be chosen.]

18

In further elucidation of this general doctrine, see First Principles, § 25.

19

In ordinary speech Development is often used as synonymous with Growth. It hence seems needful to say that Development as here and hereafter used, means increase of structure and not increase of bulk. It may be added that the word Evolution, comprehending growth as well as Development, is to be reserved for occasions when both are implied.

20

This paragraph originally formed part of a review-article on "Transcendental Physiology," published in 1857.

21

When, in 1863, the preceding chapter was written, it had not occurred to me that there needed an accompanying chapter treating of Structure. The gap left by that oversight I now fill up. In doing this there have been included certain statements which are tacitly presupposed in the last chapter, and there may also be some which overlap statements in the next chapter. I have not thought it needful so to alter adjacent chapters as to remove these slight defects: the duplicated ideas will bear re-emphasizing.

22

In connexion with this matter I add here a statement made by Prof. Foster which it is difficult to understand: "Indeed it has been observed that a dormouse actually gained in weight during a hybernating period; it discharged during this period neither urine nor fæces, and the gain in weight was the excess of oxygen taken in over the carbonic acid given out." (Text-book of Physiology, 6th ed., Part II, page 859.)

23

In the account of James Mitchell, a boy born blind and deaf, given by James Wardrop, F.R.S. (Edin. 1813), it is said that he acquired a "preternatural acuteness of touch and smell." The deaf Dr. Kitto described himself as having an extremely strong visual memory: he retained "a clear impression or image of everything at which he ever looked."

24

Here, as in sundry places throughout this chapter, the necessities of the argument have obliged me to forestall myself, by assuming the conclusion reached in a subsequent chapter, that modifications of structure produced by modifications of function are transmitted to offspring.

25

Whether the Volvox is to be classed as animal or vegetal is a matter of dispute; but its similarity to the blastula stage of many animals warrants the claim of the zoologists.

26

While the proof was in my hands there was published in Science Progress an essay by Dr. T. G. Brodie on "The Phosphorus-containing Substances of the Cell." In this essay it is pointed out that "nucleic acid is particularly characterized by its instability… In the process of purification it is extremely liable to decompose, with the result that it loses a considerable part of its phosphorus. In the second place it is most easily split up in another manner in which it loses a considerable part of its nitrogen… To avoid the latter source of error he [Miescher] found that it was necessary to keep the temperature of all solutions down to 0 °C., the whole time of the preparation." These facts tend strongly to verify the hypothesis that the nucleus is a source of perpetual molecular disturbance – not a regulating centre but a stimulating centre.

27

The writing of the above section reminded me of certain allied views which I ventured to suggest nearly 50 years ago. They are contained in the Westminster Review for April, 1852, in an article entitled "A Theory of Population deduced from the General Law of Animal Fertility." It is there suggested that the "spermatozoon is essentially a neural element, and the ovum essentially a hæmal element," or, as otherwise stated, that the "sperm-cell is co-ordinating matter and the germ-cell matter to be co-ordinated" (pp. 490-493). And along with this proposition there is given some chemical evidence tending to support it. Now if, in place of "neural" and "hæmal," we say – the element that is most highly phosphorized and the element that is phosphorized in a much smaller degree; or if, in place of co-ordinating matter and matter to be co-ordinated, we say – the matter which initiates action and the matter which is made to act; there is disclosed a kinship between this early view and the view just set forth. In the last part of this work, "Laws of Multiplication," which is developed from the essay referred to, I left out the portion containing the quoted sentences, and the evidence supporting the conclusion drawn. Partly I omitted them because the speculation did not form an essential link in the general argument, and partly because I did not see how the suggested interpretation could hold of plants as well as of animals. If, however, the alleged greater staining capacity of the male generative nucleus in plants implies, as in other cases, that the male cell has a larger proportion of the phosphorized matter than the other elements concerned, then the difficulty disappears.

As, along with the idea just named, the dropped portion of the original essay contains other ideas which seem to me worth preserving, I have thought it as well to reproduce it, in company with the chief part of the general argument as at first sketched out. It will be found in Appendix A to this volume.

28

Unfortunately the word heterogenesis has been already used as a synonym for "spontaneous generation." Save by those few who believe in "spontaneous generation," however, little objection will be felt to using the word in a sense that seems much more appropriate. The meaning above given to it covers both Metagenesis and Parthenogenesis.

29

Prof. Huxley avoids this difficulty by making every kind of Genesis a mode of development. His classification, which suggested the one given above, is as follows: —

30

The implication is that an essentially similar process occurs in those fragments of leaves used for artificial propagation. Besides the Begonias in general, I learn that various other plants are thus multiplied – Citron and orange trees, Hoya carnosa, Aucuba japonica, Clianthus puniceus, etc., etc. Bryophyllum calicinum, Rochea falcata, and Echeveria. I also learn that the following plants, among others, produce buds from their foliage leaves: —Cardamine pratensis, Nasturtium officinale, Roripa palustris, Brassica oleracea, Arabis pumila, Chelidonium majus, Nymphæa guianensis, Episcia bicolor, Chirita sivensis, Pinguicula Backeri, Allium, Gagea, Tolmia, Fritillaria, Ornithogalum, etc. In Cardamine and several others, a complete miniature plant is at once produced; in other cases bulbils or similar detachable buds.

31

Among various examples I have observed, the most remarkable were among Foxgloves, growing in great numbers and of large size, in a wood between Whatstandwell Bridge and Crich, in Derbyshire. In one case the lowest flower on the stem contained, in place of a pistil, a shoot or spike of flower-buds, similar in structure to the embryo-buds of the main spike. I counted seventeen buds on it; of which the first had three stamens, but was otherwise normal; the second had three; the third, four; the fourth, four; &c. Another plant, having more varied monstrosities, evinced excess of nutrition with equal clearness. The following are the notes I took of its structure: – 1st, or lowest flower on the stem, very large; calyx containing eight divisions, one partly transformed into a corolla, and another transformed into a small bud with bract (this bud consisted of a five-cleft calyx, four sessile anthers, a pistil, and a rudimentary corolla); the corolla of the main flower, which was complete, contained six stamens, three of them bearing anthers, two others being flattened and coloured, and one rudimentary; there was no pistil but, in place of it, a large bud, consisting of a three-cleft calyx of which two divisions were tinted at the ends, an imperfect corolla marked internally with the usual purple spots and hairs, three anthers sessile on this mal-formed corolla, a pistil, a seed vessel with ovules, and, growing to it, another bud of which the structure was indistinct. 2nd flower, large; calyx of seven divisions, one being transformed into a bud with bract, but much smaller than the other; corolla large but cleft along the top; six stamens with anthers, pistil, and seed-vessel. 3rd flower, large; six-cleft calyx, cleft corolla, with six stamens, pistil, and seed-vessel, with a second pistil half unfolded at its apex. 4th flower, large; divided along the top, six stamens. 5th flower, large; corolla divided into three parts, six stamens. 6th flower, large; corolla cleft, calyx six cleft, the rest of the flower normal. 7th, and all succeeding flowers, normal.

While this chapter is under revision, another noteworthy illustration has been furnished to me by a wall-trained pear tree which was covered in the spring by luxuriant "foreright" shoots. As I learned from the gardener, it was pruned just as the fruit was setting. A large excess of sap was thus thrown into other branches, with the result that in a number of them the young pears were made monstrous by reversion. In some cases, instead of the dried up sepals at the top of the pear, there were produced good sized leaves; and in other cases the seed-bearing core of the pear was transformed into a growth which protruded through the top of the pear in the shape of a new shoot.

32

In partial verification, Mr. Tansley writes: – "Prof. Klebs of Basel has shown that in Hydrodictyon, gametes can only be produced by the cells of a net when these are above a certain size and age; and then only under conditions unfavourable to growth, such as a feeble light or poverty of nutritive inorganic salts or absence of oxygen, or a low temperature in the water containing the plant. The presence of organic substances, especially sugar, also acts as a stimulus to the formation of gametes, and this is also the case in Vaucheria. Many other Algæ produce gametes mainly at the end of the vegetative season, when food is certainly difficult to obtain in their natural habitat, and we may well suppose that their assimilative power is waning. Where, however, as is the case in Vaucheria, the plant depends for propagation mainly on the production of fertilized eggs, we find the sexual organs often produced in conditions very favourable to vegetative growth, in opposition to those cases such as Hydrodictyon, where the chief means of propagation is by zoospores. So that side by side with, and to some extent obscuring, the principle developed above we have a clear adaptation of the production of reproductive cells to the special circumstances of the case."

33

This establishment by survival of the fittest of reproductive processes adapted to variable conditions, is indirectly elucidated by the habits of salmon. As salmon thrive in the sea and fall out of condition in fresh water (having during their sea-life not exercised the art of catching fresh-water prey), the implication is that the species would profit if all individuals ran up the rivers just before spawning time in November. Why then do most of them run up during many preceding months? Contemplation of the difficulties which lie in the way to the spawning grounds, will, I think, suggest an explanation. There are falls to be leaped and shallow rapids to be ascended. These obstacles cannot be surmounted when the river is low. A fish which starts early in the season has more chances of getting up the falls and the rapids than one which starts later; and, out of condition as it will be, may spawn, though not well. On the other hand, one which starts in October, if floods occur appropriately, may reach the upper waters and then spawn to great advantage; but in the absence of adequate rains it may fail altogether to reach the spawning grounds. Hence the species profits by an irregularity of habits adapted to meet irregular contingencies.

34

I owe to Mr. (now Sir John) Lubbock an important confirmation of this view. After stating his belief that between Crustaceans and Insects there exists a physiological relation analogous to that which exists between water vertebrata and land-vertebrata, he pointed out to me that while among Insects there is a definite limit of growth, and an accompanying definite commencement of reproduction, among Crustaceans, where growth has no definite limit, there is no definite relation between the commencement of reproduction and the decrease or arrest of growth.

35

While this chapter is passing through the press, I learn from Mr. White Cooper, that not only are near sight, long sight, dull sight, and squinting, hereditary; but that a peculiarity of vision confined to one eye is frequently transmitted: re-appearing in the same eye in offspring.

36

An instance here occurs of the way in which those who are averse to a conclusion will assign the most flimsy reasons for rejecting it. Rather than admit that the eyes of these creatures living in darkness have disappeared from lack of use, some contend that such creatures would be liable to have their eyes injured by collisions with objects, and that therefore natural selection would favour those individuals in which the eyes had somewhat diminished and were least liable to injury: the implication being that the immunity from the inflammations due to injuries would be so important a factor in life as to cause survival. And this is argued in presence of the fact that one of the most conspicuous among these blind cave-animals is a cray-fish, and that the cray-fish in its natural habitat is in the habit of burrowing in the banks of rivers holes a foot or more deep, and has its eyes exposed to all those possible blows and frictions which the burrowing involves!

37

In addition to the numerous illustrations given by Mr. Sedgwick, here is one which Colonel A. T. Fraser published in Nature for Nov. 9, 1893, concerning two Hindoo dwarfs: – "In speech and intelligence the dwarfs were indistinguishable from ordinary natives of India. From an interrogation of one of them, it appeared that he belonged to a family all the male members of which have been dwarfs for several generations. They marry ordinary native girls, and the female children grow up like those of other people. The males, however, though they develop at the normal rate until they reach the age of six, then cease to grow, and become dwarfs."

38

This remarkable case appears to militate against the conclusion, drawn a few pages back, that the increase of a peculiarity by coincidence of "spontaneous variations" in successive generations, is very improbable; and that the special superiorities of musical composers cannot have thus arisen. The reply is that the extreme frequency of the occurrence among so narrow a class as that of musical composers, forbids the interpretation thus suggested.

39

I omitted to name here a cause which may be still more potent in producing irregularity in the results of cousin-marriages. So far as I can learn, no attempt has been made to distinguish between such results as arise when the related parents from whom the cousins descend are of the same sex and those which arise when they are of different sexes. In the one case two sisters have children who intermarry; and in the other case a brother and a sister have children who intermarry. The marriages of cousins in these two cases may be quite dissimilar in their results. If there is a tendency to limitation of heredity by sex – if daughters usually inherit more from the mother than sons do, while sons inherit more from the father than from the mother, then two sisters will on the average of cases be more alike in constitution than a sister and a brother. Consequently the descendants of two sisters will differ less in their constitutions than the descendants of a brother and a sister; and marriage in the first case will be more likely to prove injurious from absence of dissimilarity in the physiological units than marriage in the second. My own small circle of friends furnishes evidence tending to verify this conclusion. In one instance two cousins who intermarried are children of two sisters, and they have no offspring. In another the cousins who intermarried are children of two brothers, and they have no offspring. In the third case the cousins were descendants of two brothers and only one child resulted.

40

A propos of this sentence one of my critics writes: – "I cannot find in this book the statement as first made that the 'life of an individual is maintained by the unequal and ever-varying actions of incident forces on its different parts.' Recent physiological work offers a startling example of the statement."

To the question contained in the first sentence the answer is that I have not made the statement in the above words, but that it is implied in the chapter entitled "The Degree of Life varies as the Degree of Correspondence," and more especially in § 36, which, towards its close, definitely involves the statement. The verifying evidence my critic gives me is this: —

"Prof. Sherrington has shown that if the sensory roots of the spinal nerves are cut one by one there is at first no general effect produced. That is to say, the remainder of the nervous system continues to function as before. This condition (lack of general effect) persists until about six pairs have been cut. With the severance of the seventh pair, however, the whole central nervous system ceases to function, so that stimulation of intact sensory nerves produces no reflex action. After a variable period, but one of many hours duration, the power of functioning is recovered. That is to say, if the sensory impulses (from the skin, &c.) reaching the central nervous system are rapidly reduced in amount, there comes a point where those remaining do not suffice to keep the structure 'awake.' After a time, however, it adjusts itself to work with the diminished supply. Similarly Strumpell describes the case of a boy 'whose sensory inlets were all paralyzed except one eye and one ear.' When these were closed he instantly fell asleep."

41

Fifty years before the discovery of the Röntgen rays and those habitually emanating from uranium, it had been observed by Moser that under certain conditions the surfaces of metals receive permanent impressions from appropriate objects placed upon them. Such facts show that the molecules of substances propagate in all directions special ethereal undulations determined by their special constitutions.

42

This classification, and the three which follow it, I quote (abridging some of them) from Prof. Agassiz's "Essay on Classification."

43

For explanations, see "Illogical Geology," Essays, Vol. I. How much we may be misled by assuming that because the remains of creatures of high types have not been found in early strata, such creatures did not exist when those strata were formed, has recently (1897) been shown by the discovery of a fossil Sea-cow in the lower Miocene of Hesse-Darmstadt. The skeleton of this creature proves that it differed from such Sirenian mammals as the existing Manatee only in very small particulars: further dwindling of disused parts being an evident cause. The same is true as regards, now, we consider that since the beginning of Miocene days this aberrant type of mammal has not much increased its divergence from the ordinary mammalian type; if we then consider how long it must have taken for this large aquatic mammal (some eight or ten feet long) to be derived by modification from a land-mammal; and if then we contemplate the probable length of the period required for the evolution of that land-mammal out of a pre-mammalian type; we seem carried back in thought to a time preceding any of our geologic records. We are shown that the process of organic evolution has most likely been far slower than is commonly supposed.