10. Inductive. We may now endeavour to see how far observation supports the deductive hypothesis that longevity is favoured by high individuation, and small expenditure, both personal and generative. And here again we must allude to the profound ignorance in which we are as to the exact potential life-period, by whatever standard it be given, of any animal. Those which we have under observation we influence abnormally, and those which we have not under observation we know little about. We must then, as well as we can, make allowance for abnormal influences, and depend largely on general impressions. A list of statements as to the longevity of different groups of organisms is hereto appended, derived from the works of many authors, and from private sources of information. It is by no means a satisfactory accumulation of data, but it is believed that under present circumstances nothing better can be drawn up.1 Lord Bacon's chapter on the same subject is added in full, in order that the reader may appreciate the state of knowledge in his time as to the question. It will be seen from many of his remarks that he had the notion that bulk favours longevity, and that personal and generative expenditure antagonize it. 1 Any trustworthy additions to these statements will be very acceptable to me. Statements as to Duration of the Individual in Organisms. ANIMALS. PROTOZOA.—Cause of death is the breaking up of the whole living substance into generative particles, or its division into two or more new individualities. Persistence of life unknown in nearly all cases. Protomyxa aurantiaca-a Moneron-is stated by Haeckel to take from 4 to 6 days in the process of division. (Monogr. of Monera. Quarterly Journal of Microsc. Science, 1869.) Amaba probably takes longer. Infusoria have been seen to divide every half hour. (H. Spencer.) Zoothamnium-a Vorticellidon-every 2 hours. (Brightwell.) *Spongilla fluviatilis dies yearly, leaving reproductive masses, the so-called seeds. CŒLENTERATA (Polyps).—Some appear to die annually or on reproduction, others continue to live and grow till mechanical causes bring death. * Hydra viridis reproduces sexually in the autumn and dies. Compound Hydrozoa live for a much longer period than one year. ECHINODERMATA, from the great variation in size of mature specimens of the same species, are inferred to die only from mechanical or accidental causes. No observations on record. 1 A letter from Mr. C. W. Peach informs me that granny,' as this Actinia is called, is still alive and well, in spite of once being accidentally buried in white-wash. VERMES (Worms).—Turbellaria, unknown longevity; they have more than a year's life. Parasitic forms have interposed periods of quiescence (encysted * Rotifera die yearly or half-yearly in some cases consequent on reproduction. ANNULATA (Ringed Worms).—None but a mechanical limit to life is apparent. From the rate of growth and size, many years of life are inferred for Lumbricus, Eunice, Aphrodite, and Ampbinome. The smaller but not the larger Oligochata die in winter after reproducing sexually. CRUSTACEA.—The larger forms (Decapoda and some Schizopoda, also Merostomata), from their great range of adult size, are inferred to continue growth long after sexual maturity, and no period of natural decay is known to be reached. Smaller forms; many die annually, in the same way as Rotifera. * Cheirocephalus diaphanus developes from the egg, reproduces, and dies in 2 to 3 months. (Observed by the writer.) * Cancer pagurus, of great size, was observed with adherent Cirrhipedia, which must have become attached subsequently to the last moult, and have taken some years in their own growth. (Communicated by Thomas Bell, Esq., F.R.S.) INSECTA.—The Imago, as a rule, lives part of a year—from 6 months to a few hours-dying on reproduction. The length of life of the larva varies greatly in closely allied forms, from 4 years or more to a week. (Coleoptera, Diptera.) * Rose-chafer (Scarabæus auratus) was kept and observed 4 years in larva and 2 years in imago. (Leo Grindon, 'Life, its Nature,' &c.) * Vanessa Cardui, usually observed to die at the end of the year, was kept by a lady 3 or 4 years. (Rev. J. G. Wood.) ? Mantis religiosa is said to attain 8 years of life. (Leo Grindon, loc. cit.) Butterflies which escape copulation are known to hybernate and live a second year, or part of it, as imagines. * Flea, 9 months in imago. A man is now in London with performing fleas, and he finds that 9 months is a very great age for them to attain. MYRIAPODA-ARACHNIDA.-The large forms are supposed to live longer than Insects, but this idea may be due to the absence of metamorphosis. MOLLUSCOIDA.-? MOLLUSCA (Snails and Mussels) are in the same case as large Crustacea as to long growth, and absence of observed period of decline. No observations. [The same Limpet might probably be observed for many years.] It is known from the rate of growth of the shell that some Mollusca must live 20 years or more. FISH.-Great variation in sizes of adults (from 10 to 100 lbs.) of the same species. They are not known to get feeble as they grow old, and many are known not to get feebler. * Carp,1 150 years old, and lively (seen by Buffon in pond of Comte de Maurepas). The same fish were seen by Duhamel. ? Pike, 267 years old—if a ring with the following inscription which was attached to it be genuine :- I am the fish which was first of all put into this lake by the hands of the Governor of the Universe, Frederick the Second, the 5th of October, 1230.' It weighed 350 lbs., and was 19 feet long. Its skeleton was exhibited at Manheim. Taken in Suabia, at Halibrun, in 1497. (Gesner, quoted by Yarrell.) 90 years old. (Pennant, quoted by Yarrell.) Murana, 60 years old, in the Roman vivaria. (Pliny, quoted by Salmon of sufficient size, according to their rate of growth, to lead AMPHIBIA.-The fish-like forms may agree with fish in their longevity. The Batrachia appear to have a period of senility and decay. * Sieboldia maxima has been in the Zoological Gardens for 10 years. ? Toad, 36 years. (Smellie, quoted by L. Grindon, loc. cit.) ? Frog, 12-16 years. (Grindon, loc. cit.) 1 Carp were observed by Yarrell to weigh 6 lbs. at 10 years; the largest he could ascertain the weight of was 18 lbs. The rate of increase is probably not uniform, diminishing with age, but never ceasing entirely. REPTILES. Some are believed to grow as long as they live, are very slow in growth, very long-lived, and very variable in average adult size; e.g. Chelonia and Crocodilia; others, as the Lacertilia, are much more constant in size, and are believed to be shorter-lived. Crocodiles, some of the sacred crocodiles of India, have been known since the Conquest. * Tortoise, from the Galapagos, was inferred to be 175 years old from its rate of growth in the Zoological Gardens, London. (Grindon.) * Tortoise, from the Cape, which had been in the Governor's garden for 80 years; it was believed to be 200 years old. (Communicated by T. Bell, Esq., F.R.S.) BIRDS. Their growth is limited; they appear to get feeble at a certain age, varying in species, and like mammals may die of old age.' *Parroquet, 120 years old at death, lived at Florence for 100 years in a noble family. (Fontenelle, quoted by Flourens, Human Longevity,' trans. by C. Martel.) * Parrot,? sp. 120 years old at death, lived in the family of Mr. W. for 80 years; it was said to be 40 when brought to Mr. W.'s great-grandfather. (Communicated.) ? Goose, 100 years. (Willoughby.) ? Falcon, large species, 162 years, from inscription on an attached ring. It was brought from the Cape in 1772. (Hufeland, The Art of Prolonging Life.') ? Raven, 180 years. (Buffon.) The following seven facts were communicated by Mr. Darwin :— * Saxicola sialis, for 10 years and more was observed to build its nest in same spot. (Amer. Jour. Sci.' vol. 30, p. 81.) *Muscicapa fusca, 9 years; same observation. * Turdus, for a longer period. *Falco borealis, 12 years. *Starling, for 8 years the same lame specimen was observed by Eckmark. * Kestrel, for 6 years the same specimen was seen. * Goldfinch, lived 23 years in confinement. (Montagu.) |