Chapter LIV: Part II (2)

It was shown in the fifteenth chapter that certain characters are antagonistic to each other or do not readily blend; hence, when two animals with antagonistic characters are crossed, it might well happen that a sufficiency of gemmules in the male alone for the reproduction of his peculiar characters, and in the female alone for the reproduction of her peculiar characters, would not be present; and in this case dormant gemmules derived from the same part in some remote progenitor might easily gain the ascendancy, and cause the reappearance of the long-lost character. For instance, when black and white pigeons, or black and white fowls, are crossed,—colours which do not readily blend,—blue plumage in the one case, evidently derived from the rock-pigeon, and red plumage in the other case, derived from the wild jungle-cock, occasionally reappear. With uncrossed breeds the same result follows, under conditions which favour the multiplication and development of certain dormant gemmules, as when animals become feral and revert to their pristine character. A certain number of gemmules being requisite for the development of each character, as is known to be the case from several spermatozoa or pollen-grains being necessary for fertilisation, and time favouring their multiplication, will perhaps account for the curious cases, insisted on by Mr. Sedgwick, of certain diseases which regularly appear in alternate generations. This likewise holds good, more or less strictly, with other weakly inherited modifications. Hence, as I have heard it remarked, certain diseases appear to gain strength by the intermission of a generation. The transmission of dormant gemmules during many successive generations is hardly in itself more improbable, as previously remarked, than the retention during many ages of rudimentary organs, or even only of a tendency to the production of a rudiment; but there is no reason to suppose that dormant gemmules can be transmitted and propagated for ever. Excessively minute and numerous as they are believed to be, an infinite number derived, during a long course of modification and descent, from each unit of each progenitor, could not be supported or nourished by the organism. But it does not seem improbable that certain gemmules, under favourable conditions, should be retained and go on multiplying for a much longer period than others. Finally, on the view here given, we certainly gain some insight into the wonderful fact that the child may depart from the type of both its parents, and resemble its grandparents, or ancestors removed by many hundreds of generations.

_Conclusion._

The hypothesis of Pangenesis, as applied to the several great classes of facts just discussed, no doubt is extremely complex, but so are the facts. The chief assumption is that all the units of the body, besides having the universally admitted power of growing by self-division, throw off minute gemmules which are dispersed through the system. Nor can this assumption be considered as too bold, for we know from the cases of graft-hybridisation that formative matter of some kind is present in the tissues of plants, which is capable of combining with that included in another individual, and of reproducing every unit of the whole organism. But we have further to assume that the gemmules grow, multiply, and aggregate themselves into buds and the sexual elements; their development depending on their union with other nascent cells or units. They are also believed to be capable of transmission in a dormant state, like seeds in the ground, to successive generations.

In a highly-organised animal, the gemmules thrown off from each different unit throughout the body must be inconceivably numerous and minute. Each unit of each part, as it changes during development, and we know that some insects undergo at least twenty metamorphoses, must throw off its gemmules. But the same cells may long continue to increase by self-division, and even become modified by absorbing peculiar nutriment, without necessarily throwing off modified gemmules. All organic beings, moreover, include many dormant gemmules derived from their grandparents and more remote progenitors, but not from all their progenitors. These almost infinitely numerous and minute gemmules are contained within each bud, ovule, spermatozoon, and pollen-grain. Such an admission will be declared impossible; but number and size are only relative difficulties. Independent organisms exist which are barely visible under the highest powers of the microscope, and their germs must be excessively minute. Particles of infectious matter, so small as to be wafted by the wind or to adhere to smooth paper, will multiply so rapidly as to infect within a short time the whole body of a large animal. We should also reflect on the admitted number and minuteness of the molecules composing a particle of ordinary matter. The difficulty, therefore, which at first appears insurmountable, of believing in the existence of gemmules so numerous and small as they must be according to our hypothesis, has no great weight.

The units of the body are generally admitted by physiologists to be autonomous. I go one step further and assume that they throw off reproductive gemmules. Thus an organism does not generate its kind as a whole, but each separate unit generates its kind. It has often been said by naturalists that each cell of a plant has the potential capacity of reproducing the whole plant; but it has this power only in virtue of containing gemmules derived from every part. When a cell or unit is from some cause modified, the gemmules derived from it will be in like manner modified. If our hypothesis be provisionally accepted, we must look at all the forms of asexual reproduction, whether occurring at maturity or during youth, as fundamentally the same, and dependent on the mutual aggregation and multiplication of the gemmules. The re-growth of an amputated limb and the healing of a wound is the same process partially carried out. Buds apparently include nascent cells, belonging to that stage of development at which the budding occurs, and these cells are ready to unite with the gemmules derived from the next succeeding cells. The sexual elements, on the other hand, do not include such nascent cells; and the male and female elements taken separately do not contain a sufficient number of gemmules for independent development, except in the cases of parthenogenesis. The development of each being, including all the forms of metamorphosis and metagenesis, depends on the presence of gemmules thrown off at each period of life, and on their development, at a corresponding period, in union with preceding cells. Such cells may be said to be fertilised by the gemmules which come next in due order of development. Thus the act of ordinary impregnation and the development of each part in each being are closely analogous processes. The child, strictly speaking, does not grow into the man, but includes germs which slowly and successively become developed and form the man. In the child, as well as in the adult, each part generates the same part. Inheritance must be looked at as merely a form of growth, like the self-division of a lowly-organised unicellular organism. Reversion depends on the transmission from the forefather to his descendants of dormant gemmules, which occasionally become developed under certain known or unknown conditions. Each animal and plant may be compared with a bed of soil full of seeds, some of which soon germinate, some lie dormant for a period, whilst others perish. When we hear it said that a man carries in his constitution the seeds of an inherited disease, there is much truth in the expression. No other attempt, as far as I am aware, has been made, imperfect as this confessedly is, to connect under one point of view these several grand classes of facts. An organic being is a microcosm—a little universe, formed of a host of self-propagating organisms, inconceivably minute and numerous as the stars in heaven.

REFERENCES

[1] This hypothesis has been severely criticised by many writers, and it will be fair to give references to the more important articles. The best essay which I have seen is by Prof. Delpino, entitled ‘Sulla Darwiniana Teoria della Pangenesi, 1869,’ of which a translation appeared in ‘Scientific Opinion,’ Sept. 29th, 1869, and the succeeding numbers. He rejects the hypothesis, but criticises it fairly, and I have found his criticisms very useful. Mr. Mivart (‘Genesis of Species,’ 1871, chap. x.) follows Delpino, but adds no new objections of any weight. Dr. Bastian (‘The Beginnings of Life,’ 1872, vol. ii. p. 98) says that the hypothesis “looks like a relic of the old rather than a fitting appanage of the new evolution philosophy.” He shows that I ought not to have used the term “pangenesis,” as it had been previously used by Dr. Gros in another sense. Dr. Lionel Beale (‘Nature,’ May 11th, 1871, p. 26) sneers at the whole doctrine with much acerbity and some justice. Prof. Wigand (‘Schriften der Gesell. der gesammt. Naturwissen. zu Marburg,’ B. ix. 1870) considers the hypothesis as unscientific and worthless. Mr. G. H. Lewes (‘Fortnightly Review,’ Nov. 1st, 1868, p. 503) seems to consider that it may be useful: he makes many good criticisms in a perfectly fair spirit. Mr. F. Galton, after describing his valuable experiments (‘Proc. Royal Soc.,’ vol. xix. p. 393) on the intertransfusion of the blood of distinct varieties of the rabbit, concludes by saying that in his opinion the results negative beyond all doubt the doctrine of Pangenesis. He informs me that subsequently to the publication of his paper he continued his experiments on a still larger scale for two more generations, without any sign of mongrelism showing itself in the very numerous offspring. I certainly should have expected that gemmules would have been present in the blood, but this is no necessary part of the hypothesis, which manifestly applies to plants and the lowest animals. Mr. Galton, in a letter to ‘Nature’ (April 27th, 1871, p. 502), also criticises various incorrect expressions used by me. On the other hand, several writers have spoken favourably of the hypothesis, but there would be no use in giving references to their articles. I may, however, refer to Dr. Ross’ work, ‘The Graft Theory of Disease; being an application of Mr. Darwin’s hypothesis of Pangenesis,’ 1872, as he gives several original and ingenious discussions.

[2] Quoted by Paget, ‘Lectures on Pathology,’ 1853, p. 159.

[3] Dr. Lachmann, also, observes (‘Annals and Mag. of Nat. History,’ 2nd series, vol. xix. 1857, p. 231) with respect to infusoria, that “fissation and gemmation pass into each other almost imperceptibly.” Again, Mr. W. C. Minor (‘Annals and Mag. of Nat. Hist.,’ 3rd series, vol. xi. p. 328) shows that with Annelids the distinction that has been made between fission and budding is not a fundamental one. _See also_ Professor Clark’s work ‘Mind in Nature,’ New York, 1865, pp. 62, 94.

[4] _See_ Bonnet, ‘Œuvres d’Hist. Nat.,’ tom. v., 1781, p. 339, for remarks on the budding-out of the amputated limbs of Salamanders.

[5] Paget, ‘Lectures on Pathology,’ 1853, p. 158.

[6] Ibid., pp. 152, 164.

[7] Translated in ‘Annals and Mag. of Nat. Hist.,’ April 1870, p. 272.

[8] Bischoff, as quoted by von Siebold, “Ueber Parthenogenesis,” ‘Sitzung der math. phys. Classe.’ Munich, Nov. 4th, 1871, p. 240. _See also_ Quatrefages, ‘Annales des Sc. Nat. Zoolog.,’ 3rd series, 1850, p. 138.

[9] ‘On the Asexual Reproduction of Cecidomyide Larvæ,’ translated in ‘Annals and Mag. of Nat. Hist.,’ March 1866, pp. 167, 171.

[10] Prof. Allman speaks (‘Transact. R. Soc. of Edinburgh,’ vol. xxvi., 1870, p. 102) decisively on this head with respect to the Hydroida: he says, “It is a universal law in the succession of zooids, that no retrogression ever takes place in the series.”

[11] ‘Annals and Mag. of Nat. Hist.,’ 2nd series, vol. xx., 1857, pp. 153-455.

[12] ‘Annales des Sc. Nat.,’ 3rd series, 1850, tom. xiii.

[13] ‘Transact. Phil. Soc.,’ 1851, pp. 196, 208, 210; 1853 pp. 245, 247.

[14] ‘Beitrage zur Kenntniss,’ etc., 1844, s. 345.

[15] ‘Nouvelles Archives du Muséum,’ tom. i. p. 27.

[16] As quoted by Sir J. Lubbock in ‘Nat. Hist. Review,’ 1862, p. 345. Weijenbergh also raised (‘Nature,’ Dec. 21st, 1871, p. 149) two successive generations from unimpregnated females of another lepidopterous insect, _Liparis dispar._ These females did not produce at most one-twentieth of their full complement of eggs, and many of the eggs were worthless. Moreover the caterpillars raised from these unfertilised eggs “possessed far less vitality” than those from fertilised eggs. In the third parthenogenetic generation not a single egg yielded a caterpillar.

[17] ‘Entwickelungsgeschichte der Siphonophora,’ 1869, p. 73.

[18] Spallanzani, ‘An Essay on Animal Reproduction,’ translated by Dr. Maty, 1769, p. 79. Bonnet, ‘Œuvres d’Hist. Nat.,’ tom. v., part i., 4to. edit., 1781, pp. 343, 350.

[19] Vulpian, as quoted by Prof. Faivre, ‘La Variabilité des Espèces,’ 1868, p. 112.

[20] Dr. P. Hoy, ‘The American Naturalist,’ Sept. 1871, p. 579.

[21] Dr. Gunther, in Owen’s ‘Anatomy of Vertebrates,’ vol. i., 1866, p. 567. Spallanzani has made similar observations.

[22] A thrush was exhibited before the British Association at Hull in 1853 which had lost its tarsus, and this member, it was asserted, had been thrice reproduced; having been lost, I presume, each time by disease. Sir J. Paget informs me that he feels some doubt about the facts recorded by Sir J. Simpson (‘Monthly Journal of Medical Science,’ Edinburgh, 1848, new series, vol. ii., p. 890) of the re-growth of limbs in the womb in the case of man.

[23] ‘Atti della Soc. Ital. di Sc. Nat.,’ vol. xi., 1869, p. 493.

[24] Lessona states that this is so in the paper just referred to. _See also_ ‘The American Naturalist,’ Sept. 1871, p. 579.

[25] ‘Comptes Rendus,’ Oct. 1st, 1866, and June, 1867.

[26] Bonnet, ‘Oeuvres Hist. Nat.,’ vol. v., p. 294, as quoted by Prof. Rolleston in his remarkable address to the 36th annual meeting of the British Medical Association.

[27] ‘Proc. Boston Soc. of Nat. Hist.,’ vol. xii., 1868-69, p. 1.

[28] ‘Transact. Linn. Soc.,’ vol. xxiv., 1863, p. 62.

[29] ‘Parthenogenesis,’ 1849, pp. 25, 26. Prof. Huxley has some excellent remarks (‘Medical Times,’ 1856, p. 637) on this subject in reference to the development of star-fishes, and shows how curiously metamorphosis graduates into gemmation or zoid-formation, which is in fact the same as metagenesis.

[30] Prof. J. Reay Greene, in Günther’s ‘Record of Zoolog. Lit.,’ 1865, p. 625.

[31] Fritz Müller, ‘Für Darwin,’ 1864, s. 65, 71. The highest authority on crustaceans, Prof. Milne-Edwards, insists (‘Annal. des Sci. Nat.,’ 2nd series, Zoolog., tom. iii., p. 322) on the difference in the metamorphosis of closely-allied genera.

[32] Prof. Allman, in ‘Annals and Mag. of Nat. Hist.,’ 3rd series, vol. xiii., 1864, p. 348; Dr. S. Wright, ibid., vol. viii., 1861, p. 127. _See also_ p. 358 for analogous statements by Sars.

[33] ‘Tissus Vivants,’ 1866, p. 22.

[34] ‘Cellular Pathology,’ translated by Dr. Chance, 1860, pp. 14, 18, 83, 460.

[35] Paget, ‘Surgical Pathology,’ vol. i., 1853, pp. 12-14.

[36] Ibid., p. 19.

[37] _See_ Prof. Mantegazza’s interesting work, ‘Degli innesti Animali,’ etc., Milano, 1865, p. 51, tab. 3.

[38] ‘De la Production Artificielle des Os,’ p. 8.

[39] Isidore Geoffroy Saint-Hilaire, ‘Hist. des Anomalies,’ tom. ii., pp. 549, 560, 562; Virchow, ibid., p. 484. Lawson Tait, ‘The Pathology of Diseases of the Ovaries,’ 1874, pp. 61, 62.

[40] For the most recent classification of cells, _see_ Ernst Hackel, ‘Generelle Morpholog.,’ B. ii., 1866, s. 275.

[41] Dr. W. Turner, ‘The Present Aspect of Cellular Pathology,’ ‘Edinburgh Medical Journal,’ April 1863.

[42] Mr. G. H. Lewes (‘Fortnightly Review,’ Nov. 1st, 1868, p. 506) remarks on the number of writers who have advanced nearly similar views. More than two thousand years ago Aristotle combated a view of this kind, which, as I hear from Dr. W. Ogle, was held by Hippocrates and others. Ray, in his ‘Wisdom of God’ (2nd edit., 1692, p. 68), says that “every part of the body seems to club and contribute to the seed.” The “organic molecules” of Buffon (‘Hist. Nat. Gen.,’ edit. of 1749, tom. ii., pp. 54, 62, 329, 333, 420, 425) appear at first sight to be the same as the gemmules of my hypothesis, but they are essentially different. Bonnet (‘Œuvres d’Hist. Nat.,’ tom. v., part i., 1781, 4to edit., p. 334) speaks of the limbs having germs adapted for the reparation of all possible losses; but whether these germs are supposed to be the same with those within buds and the sexual organs is not clear. Prof. Owen says (‘Anatomy of Vertebrates,’ vol. iii., 1868, p. 813) that he fails to see any fundamental difference between the views which he propounded in his ‘Parthenogenesis’ (1849, pp. 5-8), and which he now considers as erroneous, and my hypothesis of pangenesis: but a reviewer (‘Journal of Anat. and Phys.,’ May 1869, p. 441) shows how different they really are. I formerly thought that the “physiological units” of Herbert Spencer (‘Principles of Biology,’ vol. i., chaps. iv. and viii., 1863-64) were the same as my gemmules, but I now know that this is not the case. Lastly, it appears from a review of the present work by Prof. Mantegazza (‘Nuova Antologia, Maggio,’ 1868), that he (in his ‘Elementi di Igiene,’ Ediz. iii., p. 540) clearly foresaw the doctrine of pangenesis.

[43] Mr. Lowne has observed (‘Journal of Queckett Microscopical Club,’ Sept. 23rd, 1870) certain remarkable changes in the tissues of the larva of a fly, which makes him believe “it possible that organs and organisms are sometimes developed by the aggregation of excessively minute gemmules, such as those which Mr. Darwin’s hypothesis demands.”

[44] ‘Annales des Sc. Nat.,’ 3rd series, Bot., tom. xiv., 1850, p. 244.

[45] ‘Disease Germs,’ p. 20.

[46] _See_ some very interesting papers on this subject by Dr. Beale, in ‘Medical Times and Gazette,’ Sept. 9th, 1865, pp. 273, 330.

[47] Third Report of the R. Comm. on the Cattle Plague, as quoted in ‘Gardener’s Chronicle,’ 1866, p. 446.

[48] Mr. F. Buckland found 6,867,840 eggs in a cod-fish (‘Land and Water,’ 1868, p. 62). An Ascaris produces about 64,000,000 eggs (Carpenter’s ‘Comp. Phys.,’ 1854, p. 590). Mr. J. Scott, of the Royal Botanic Garden of Edinburgh, calculated, in the same manner as I have done for some British Orchids (‘Fertilisation of Orchids,’ p. 344), the number of seeds in a capsule of an Acropera and found the number to be 371,250. Now this plant produces several flowers on a raceme, and many racemes during a season. In an allied genus, Gongora, Mr. Scott has seen twenty capsules produced on a single raceme; ten such racemes on the Acropera would yield above seventy-four millions of seed.

[49] Paget, ‘Lectures on Pathology,’ p. 27; Virchow, ‘Cellular Pathology,’ translated by Dr. Chance, pp. 123, 126, 294. Claude Bernard, ‘Des Tissus Vivants,’ pp. 177, 210, 337; Müller, ‘Physiology,’ Eng. translat., p. 290.

[50] Prof. Ray Lankester has discussed several of the points here referred to as bearing on pangenesis, in his interesting essay, ‘On Comparative Longevity in Man and the Lower Animals,’ 1870, pp. 33, 77, etc.

[51] Dr. Ross refers to this subject in his ‘Graft Theory of Disease,’ 1872, p. 53.

[52] Virchow, ‘Cellular Pathology,’ translated by Dr. Chance, 1860, pp. 60, 162, 245, 441, 454.

[53] Ibid., pp. 412-426.

[54] _See_ some good criticisms on this head by Delpino and by Mr. G. H. Lewes in the ‘Fortnightly Review,’ Nov. 1st, 1868, p. 509.

[55] Mr. Herbert Spencer (‘Principles of Biology,’ vol. ii., p. 430) has fully discussed this antagonism.

[56] The male salmon is known to breed at a very early age. The Triton and Siredon, whilst retaining their larval branchiæ, according to Filippi and Duméril (‘Annals and Mag. of Nat. Hist.,’ 3rd series, 1866, p. 157) are capable of reproduction. Ernst Haeckel has recently (‘Monatsbericht Akad. Wiss. Berlin,’ Feb. 2nd, 1865) observed the surprising case of a medusa, with its reproductive organs active, which produces by budding a widely different form of medusa; and this latter also has the power of sexual reproduction. Krohn has shown (‘Annals and Mag. of Nat. Hist.,’ 3rd series, vol. xix., 1862, p. 6) that certain other medusæ, whilst sexually mature, propagate by gemmæ. _See also_ Kolliker, ‘Morphologie und Entwickelungsgeschichte des Pennatulidenstammes,’ 1872, p. 12.

[57] _See_ his excellent discussion on this subject in ‘Nouvelles Archives du Museum,’ tom. i., p. 151.

[58] ‘Proc. Boston Soc. of Nat. Hist.,’ republished in ‘Scientific Opinion,’ Nov. 10th, 1869, p. 488.

[59] Todd’s ‘Cyclop. of Anat. and Phys.,’ vol. iv., 1849-52, p. 975.

[60] ‘Compte Rendus,’ Nov. 14th, 1865, p. 800.

[61] As previously remarked by Quatrefages, in his ‘Métamorphoses de l’Homme,’ etc., 1862, p. 129.

[62] Günther’s ‘Zoological Record,’ 1864, p. 279.

[63] Sedgwick, ‘Medico-Chirurg. Review,’ April 1863, p. 454.

[64] Isid. Geoffroy Saint-Hilaire, ‘Hist. des Anomalies,’ tom. i., 1832, pp. 435, 657; and tom. ii., p. 560.

[65] Virchow, ‘Cellular Pathology,’ 1860, p. 66.

[66] Müller’s ‘Phys.,’ Eng. Translat., vol. i., 1833, p. 407. A case of this kind has lately been communicated to me.

[67] Dr. Fürbringer, ‘Die Knochen etc. bei den schlangenähnlichen Sauriern,’ as reviewed in ‘Journal of Anat. and Phys.,’ May 1870, p. 286.

[68] Moquin-Tandon, ‘Tératologie Vég.,’ 1841, pp. 218, 220, 353. For the case of the pea, _see_ ‘Gardener’s Chronicle,’ 1866, p. 897. With respect to pollen within ovules, _see_ Dr. Masters in ‘Science Review,’ Oct. 1873, p. 369. The Rev. J. M. Berkeley describes a bud developed on a petal of a Clarkia, in ‘Gardener’s Chronicle,’ April 28th, 1866.

[69] _See_ some remarks to this effect by Sir H. Holland in his ‘Medical Notes,’ 1839, p. 32.

[70] This is the view taken by Prof. Haeckel, in his ‘Generelle Morphologie’ (B. ii. s. 171), who says: “Lediglich die partielle Identität der specifisch constituirten Materie im elterlichen und im kindlichen Organismus, die Theilung dieser Materie bei der Fortpflanzung, ist die Ursache der Erblichkeit.”

[71] In these remarks I, in fact, follow Naudin, who speaks of the elements or essences of the two species which are crossed. _ See_ his excellent memoir in the ‘Nouvelles Archives du Muséum,’ tom. i., p. 151.