The Beauties of Nature, and the Wonders of the World We Live In Part 5

LENGTH OF LIFE

How little we yet know of the life-history of Animals is ill.u.s.trated by the vagueness of our information as to the age to which they live.

Professor Lankester[18] tells us that "the paucity and uncertainty of observations on this cla.s.s of facts is extreme." The Rabbit is said to reach 10 years, the Dog and Sheep 10-12, the Pig 20, the Horse 30, the Camel 100, the Elephant 200, the Greenland Whale 400 (?): among Birds, the Parrot to attain 100 years, the Raven even more. The Atur Parrot mentioned by Humboldt, talked, but could not be understood, because it spoke in the language of an extinct Indian tribe. It is supposed from their rate of growth that among Fish the Carp is said to reach 150 years; and a Pike, 19 feet long, and weighing 350 lbs., is said to have been taken in Suabia in 1497 carrying a ring, on which was inscribed, "I am the fish which was first of all put into the lake by the hands of the Governor of the Universe, Frederick the Second, the 5th Oct. 1230." This would imply an age of over 267 years. Many Reptiles are no doubt very long-lived. A Tortoise is said to have reached 500 years. As regards the lower animals, the greatest age on record is that of Sir J. Dalzell's Sea Anemone, which lived for over 50 years. Insects are generally short-lived; the Queen Bee, however, is said by Aristotle, whose statement has not been confirmed by recent writers, to live 7 years. I myself had a Queen Ant which attained the age of 15 years.

The May Fly (Ephemera) is celebrated as living only for a day, and has given its name to all things short-lived. The statement usually made is, indeed, very misleading, for in its larval condition the Ephemera lives for weeks. Many writers have expressed surprise that in the perfect state its life should be so short. It is, however, so defenceless, and, moreover, so much appreciated by birds and fish, that unless they laid their eggs very rapidly none would perhaps survive to continue the species.

Many of these estimates are, as will be seen, very vague and doubtful, so that we must still admit with Bacon that, "touching the length and shortness of life in living creatures, the information which may be had is but slender, observation is negligent, and tradition fabulous. In tame creatures their degenerate life corrupteth them, in wild creatures their exposing to all weathers often intercepteth them."

ON INDIVIDUALITY

When we descend still lower in the animal scale, the consideration of this question opens out a very curious and interesting subject connected with animal individuality. As regards the animals with which we are most familiar no such question intrudes. Among quadrupeds and birds, fishes and reptiles, there is no difficulty in deciding whether a given organism is an individual, or a part of an individual. Nor does the difficulty arise in the case of most insects. The Bee or b.u.t.terfly lays an egg which develops successively into a larva and pupa, finally producing Bee or b.u.t.terfly. In these cases, therefore, the egg, larva, pupa, and perfect Insect, are regarded as stages in the life of a single individual. In certain gnats, however, the larva itself produces young larvae, each of which develops into a gnat, so that the egg produces not one gnat but many gnats.

The difficulty of determining what const.i.tutes an individual becomes still greater among the Zoophytes. These beautiful creatures in many cases so closely resemble plants, that until our countryman Ellis proved them to be animals, Crabbe was justified in saying--

Involved in seawrack here we find a race, Which Science, doubting, knows not where to place; On sh.e.l.l or stone is dropped the embryo seed, And quickly vegetates a vital breed.

We cannot wonder that such organisms were long regarded as belonging to the vegetable kingdom. The cups which terminate the branches contain, however, an animal structure, resembling a small Sea Anemone, and possessing arms which capture the food by which the whole colony is nourished. Some of these cups, moreover, differ from the rest, and produce eggs. These then we might be disposed to term ovaries. But in many species they detach themselves from the group and lead an independent existence. Thus we find a complete gradation from structures which, regarded by themselves, we should unquestionably regard as mere organs, to others which are certainly separate and independent beings.

[Ill.u.s.tration: Fig. 2.--Bougainvillea fruticosa; natural size. (After Allman.)]

Fig. 2 represents, after Allman, a colony of Bougainvillea fruticosa of the natural size. It is a British species, which is found growing on buoys, floating timber, etc., and, says Allman, "When in health and vigour, offers a spectacle unsurpa.s.sed in interest by any other species--every branchlet crowned by its graceful hydranth, and budding with Medusae in all stages of development (Fig. 3), some still in the condition of minute buds, in which no trace of the definite Medusa-form can yet be detected; others, in which the outlines of the Medusa can be distinctly traced within the transparent ectotheque (external layer); others, again, just casting off this thin outer pellicle, and others completely freed from it, struggling with convulsive efforts to break loose from the colony, and finally launched forth in the full enjoyment of their freedom into the surrounding water. I know of no form in which so many of the characteristic features of a typical hydroid are more finely expressed than in this beautiful species."

[Ill.u.s.tration: Fig. 3.--Bougainvillea fruticosa; magnified to show development.]

Fig. 4 represents the Medusa or free form of this beautiful species.

[Ill.u.s.tration: Fig. 4.--Bougainvillea fruticosa, Medusa-form.]

If we pa.s.s to another great group of Zoophytes, that of the Jelly-fishes, we have a very similar case. For our first knowledge of the life-history of these Zoophytes we are indebted to the Norwegian naturalist Sars. Take, for instance, the common Jelly-fish (Medusa aurita) (Fig. 5) of our sh.o.r.es.

The egg is a pear-shaped body (_1_), covered with fine hairs, by the aid of which it swims about, the broader end in front. After a while it attaches itself, not as might have been expected by the posterior but by the anterior extremity (_2_). The cilia then disappear, a mouth is formed at the free end, tentacles, first four (_3_), then eight, and at length as many as thirty (_4_), are formed, and the little creature resembles in essentials the freshwater polyp (Hydra) of our ponds.

[Ill.u.s.tration: Fig. 5.--Medusa aurita, and progressive stages of development.]

At the same time transverse wrinkles (_4_) are formed round the body, first near the free extremity and then gradually descending. They become deeper and deeper, and develop lobes or divisions one under the other, as at _5_. After a while the top ring (and subsequently the others one by one) detaches itself, swims away, and gradually develops into a Medusa (_6_). Thus, then, the life-history is very similar to that of the Hydroids, only that while in the Hydroids the fixed condition is the more permanent, and the free swimming more transitory, in the Medusae, on the contrary, the fixed condition is apparently only a phase in the production of the free swimming animal. In both the one and the other, however, the egg gives rise not to one but to many mature animals.

Steenstrup has given to these curious phenomena, many other cases of which occur among the lower animals, and to which he first called attention, the name of alternations of generations.

In the life-history of Infusoria (so called because they swarm in most animal or vegetable infusions) similar difficulties encounter us. The little creatures, many of which are round or oval in form, from time to time become constricted in the middle; the constriction becomes deeper and deeper, and at length the two halves twist themselves apart and swim away. In this case, therefore, there was one, and there are now two exactly similar; but are these two individuals? They are not parent and offspring--that is clear, for they are of the same age; nor are they twins, for there is no parent. As already mentioned, we regard the Caterpillar, Chrysalis, and b.u.t.terfly as stages in the life-history of a single individual. But among Zoophytes, and even among some insects, one larva often produces several mature forms. In some species these mature forms remain attached to the larval stock, and we might be disposed to regard the whole as one complex organism. But in others they detach themselves and lead an independent existence.

These considerations then introduce much difficulty into our conception of the idea of an Individual.

ANIMAL IMMORTALITY

But, further than this, we are confronted by by another problem. If we regard a ma.s.s of coral as an individual because it arises by continuous growth from a single egg, then it follows that some corals must be thousands of years old.

Some of the lower animals may be cut into pieces, and each piece will develop into an entire organism. In fact the realisation of the idea of an individual gradually becomes more and more difficult, and the continuity of existence, even among the highest animals, gradually forces itself upon us. I believe that as we become more rational, as we realise more fully the conditions of existence, this consideration is likely to have important moral results.

It is generally considered that death is the common lot of all living beings. But is this necessarily so? Infusoria and other unicellular animals multiply by division. That is to say, if we watch one for a certain time, we shall observe, as already mentioned, that a constriction takes place, which grows gradually deeper and deeper, until at last the two halves become quite detached, and each swims away independently. The process is repeated over and over again, and in this manner the species is propagated. Here obviously there is no birth and no death. Such creatures may be killed, but they have no natural term of life. They are, in fact, theoretically immortal. Those which lived millions of years ago may have gone on dividing and subdividing, and in this sense mult.i.tudes of the lower animals are millions of years old.

FOOTNOTES:

[15] Address to Microscopical Society, 1890.

[16] _Ants, Bees, and Wasps_, and _The Senses of Animals_.

[17] Prof. Drummond (_Tropical Africa_) dwells with great force on the manner in which the soil of Central Africa is worked up by the White Ants.

[18] Lankester, _Comparative Longevity_. See also Weismann, _Duration of Life_.

CHAPTER IV

ON PLANT LIFE

Flower in the crannied wall, I pluck you out of the crannies, I hold you here, root and all, in my hand, Little flower--but _if_ I could understand What you are, root and all, and all in all, I should know what G.o.d and man is.

TENNYSON.

CHAPTER IV

ON PLANT LIFE

We are told that in old days the Fairies used to give presents of Flowers and Leaves to those whom they wished to reward, or whom they loved best; and though these gifts were, it appears, often received with disappointment, still it will probably be admitted that flowers have contributed more to the happiness of our lives than either gold or silver or precious stones; and that our happiest days have been spent out-of-doors in the woods and fields, when we have

... found in every woodland way The sunlight tint of Fairy Gold.[19]

To many minds Flowers acquired an additional interest when it was shown that there was a reason for their colour, size, and form--in fact, for every detail of their organisation. If we did but know all that the smallest flower could tell us, we should have solved some of the greatest mysteries of Nature. But we cannot hope to succeed--even if we had the genius of Plato or Aristotle--without careful, patient, and reverent study. From such an inquiry we may hope much; already we have glimpses, enough to convince us that the whole history will open out to us conceptions of the Universe wider and grander than any which the Imagination alone would ever have suggested.

Attempts to explain the forms, colours, and other characteristics of animals and plants are by no means new. Our Teutonic forefathers had a pretty story which explained certain points about several common plants.

Balder, the G.o.d of Mirth and Merriment, was, characteristically enough, regarded as deficient in the possession of immortality. The other divinities, fearing to lose him, pet.i.tioned Thor to make him immortal, and the prayer was granted on condition that every animal and plant would swear not to injure him. To secure this object, Nanna, Balder's wife, descended upon the earth. Loki, the G.o.d of Envy, followed her, disguised as a crow (which at that time were white), and settled on a little blue flower, hoping to cover it up, so that Nanna might overlook it. The flower, however, cried out "forget-me-not, forget-me-not," and has ever since been known under that name. Loki then flew up into an oak and sat on a mistletoe. Here he was more successful. Nanna carried off the oath of the oak, but overlooked the mistletoe. She thought, however, and the divinities thought, that she had successfully accomplished her mission, and that Balder had received the gift of immortality.

One day, supposing Balder proof, they amused themselves by shooting at him, posting him against a Holly. Loki tipped an arrow with a piece of Mistletoe, against which Balder was not proof, and gave it to Balder's brother. This, unfortunately, pierced him to the heart, and he fell dead. Some drops of his blood spurted on to the Holly, which accounts for the redness of the berries; the Mistletoe was so grieved that she has ever since borne fruit like tears; and the crow, whose form Loki had taken, and which till then had been white, was turned black.

This pretty myth accounts for several things, but is open to fatal objections.

Recent attempts to explain the facts of Nature are not less fascinating, and, I think, more successful.

Why then this marvellous variety? this inexhaustible treasury of beautiful forms? Does it result from some innate tendency in each species? Is it intentionally designed to delight the eye of man? Or has the form and size and texture some reference to the structure and organisation, the habits and requirements of the whole plant?