CHAPTER VI.
Every organism a colony—What is a paradox?—An organ is an independent individual, and a dependent one—A branch of coral—A colony of polypes—The Siphonophora—Universal dependence—Youthful aspirings—Our interest in the youth of great men—Genius and labour—Cuvier’s college life; his appearance in youth; his arrival in Paris—Cuvier and Geoffrey St. Hilaire—Causes of Cuvier’s success—One of his early ambitions—M. le Baron—Omnia vincit labor—Conclusion.
That an animal Organism is made up of several distinct organs, and these the more numerous in proportion to the rank of the animal in the scale of beings, is one of those familiar facts which have their significance concealed from us by familiarity. But it is only necessary to express this fact in language slightly altered, and to say that an animal Organism is made up of several distinct individuals, and our attention is at once arrested. Doubtless, it has a paradoxical air to say so; but Natural History is full of paradoxes; and you are aware that a paradox is far from being necessarily an absurdity, as some inaccurate writers would lead us to suppose: the word meaning simply, “contrary to what is thought,”—a meaning by no means equivalent to “contrary to what is the fact.” It is paradoxical to call an animal an aggregate of individuals; but it is so because our thoughts are not very precise on the subject of individuality—one of the many abstractions which remain extremely vague. To justify this application of the word individual to every distinct organ would be difficult in ordinary speech, but in philosophy there is ample warrant for it.
An organ, in the physiological sense, is an instrument whereby certain functions are performed. In the morphological sense, it arises in a differentiation, or setting apart, of a particular portion of the body for the performance of particular functions—a group of cells, instead of being an exact repetition of all the other cells, takes on a difference and becomes distinguished from the rest as an organ.[5]
Combining these two meanings, we have the third, or philosophical sense of the word, which indicates that every organ is an individual existence, dependent more or less upon other organs for its maintenance and activity, yet biologically distinct. I do not mean that the heart will live independent of the body—at least, not for long, although it does continue to live and manifest its vital activity for some time after the animal’s death; and, in the cold-blooded animals, even after removal from the body. Nor do I mean that the legs of an animal will manifest vivacity after amputation; although even the legs of a man are not dead for some time after amputation; and the parts of some of the lower animals are often vigorously independent. Thus I have had the long tentacles of a Terebella (a marine worm) living and wriggling for a whole week after amputation.[6] In speaking of the independence of an organ, I must be understood to mean a very dependent independence: because, strictly speaking, absolute independence is nowhere to be found; and, in the case of an organ, it is of course dependent on other organs for the securing, preparing, and distributing of its necessary nutriment. The tentacles of my Terebella could find no nutriment, and they perished from the want of it, as the Terebella itself would have perished under like circumstances. The frog’s heart now beating on our table with such regular systole and diastole, as if it were pumping the blood through the living animal, gradually uses up all its force; and since this force is not replaced, the beatings gradually cease. A current of electricity will awaken its activity, for a time; but, at last, every stimulus will fail to elicit a response. The heart will then be dead, and decomposition will begin.
Dependent, therefore, every organ must be on some other organs. Let us see how it is also independent; and for this purpose we glance, as usual, at the simpler forms of Life to make the lesson easier. Here is a branch of coral, which you know to be in its living state a colony of polypes. Each of these multitudinous polypes is an individual, and each exactly resembles the other. But the whole colony has one nutritive fluid in common. They are all actively engaged in securing food, and the labours of each enrich all. It is animal Socialism of the purest kind—there are no rich and no poor, neither are there any idlers. Formerly, the coral-branch was regarded as one animal—an individual; and a tree was and is commonly regarded as one plant—an individual. But no zoologist now is unaware of the fact that each polype on the branch is a distinct individual, in spite of its connections with the rest; and philosophic botanists are agreed that the tree is a colony of individual plants—not one plant.
Fig. 20.
Campanularia (Magnified, and Natural Size).
Let us pass from the coral to the stem of some other polype, say a Campanularia. Here is the representation of such a stem, of the natural size, and beside it a tiny twig much magnified. You observe the ordinary polype issuing from one of the capsules, and expanding its coronal of tentacles in the water. The food it secures will pass along the digestive tract to each of the other capsules. Under the microscope, you may watch this oscillation of the food. But your eye detects a noticeable difference between this polype in its capsule, and the six semi-transparent masses in the second capsule: although the two capsules are obviously identical, they are not the same: a differentiation has taken place. Perhaps you think that six polypes are here crowding into one capsule? Error! If you watch with patience, or if you are impatient yet tolerably dexterous, you may press these six masses out, and then will observe them swim away, so many tiny jelly-fish. Not polypes at all, but jelly-fish, are in this capsule: and these in due time will produce polypes, like that one now waving its tentacles.