Specific Nature of Life. ... 213 therefore sensible; and all sensible things which are apprehended by opinion and sense are in process of creation and created. Now that which is created must of necessity be created by a cause. . . . He put intelligence in soul, and soul in body, and framed the universe to be the best and fairest work in the order of Nature."1 Coming to our own day, Charles Darwin says-"To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes like those determining the birth and death of an individual.” 2 Very well, life and death are traced through secondary causes to Divine Will. Life is, to science, an ultimate fact; for which science can only conjecturally account. Another student writes, leading us 66 to the power of apprehending the unity which underlies the diversity of animal structures; to show in those structures the evidence of a predetermining will; producing them in reference to final purpose; and to indicate the direction and degrees in which organisation, in subserving such will, rises from the general to the particular."3 Here we have the initial fact-production, and design: the initial fact rendered law possible; design bound that law, Providence, as an elastic band round the universe of general and particular application. "4 For the specific nature and continuance of life, the best arguments are facts given by accurate observers :-"It has been deemed no mean result of comparative anatomy to have pointed out the analogy between the shark's skeleton and the human embryo, in their histological conditions; and no doubt it is a very interesting_one.' This analogy is not inconsistent with the observed tendency of offspring to differ from the parent; nor with the stranger fact-"This tendency and its results are independent of internal volition and external influence." 5 Thus we are led to the great truth-"Every species is such ab initio, and takes its own course to the full manifestation of its specific characters agreeable with the nature originally impressed upon the 1 "Timæus : " translated by Rev. B. Jowett. 2 66 3 Anatomy of Vertebrates," vol. i. p. v. Introd.: Owen. germ. A perch, a newt, a dog, a man, do not begin to be such only when the embryologist discerns the dawnings of respective specific characters. The embryo derived its nature, and the potency of self-development according to the specific pattern, from the moment of impregnation; and each step of development moves to that consummation as its end and aim."1 "An orderly succession according to law, and also progressive or in the ascending course, is evident from actual knowledge of extinct species; " 2 but none can say why circulation in the embryo of lizard, of fowl, of beast, is like that of a fish in its simplicity, but far from being identical. "It is proved that no germ, animal or vegetal, contains the slightest rudiment, trace, or indication of the future organism-since the microscope has shown us that the first process set up in every fertilised germ is a process of repeated spontaneous fissions, ending in the production of a mass of cells, not one of which exhibits any special character; there seems no alternative but to conclude that the partial organisation at any moment subsisting in a growing embryo, is transformed by the agencies acting on it into the succeeding phase of organisation, and this into the next, until, through ever-increasing complexities, the ultimate form is reached." 3 The fact is established, the operation of secondary causes is due to a great master Principle by whose will and power the waters teem with swarms of living things, and birds fly above the earth :— "Young fresh blood. Keeps ever circulating still In water, in the earth, in air, In wet, dry warm, cold, everywhere Faust. Living beings possess at least six leading characteristics. 1. Assimilation -the power of taking in external materials and converting them into substances for building up fresh tissue and repairing waste. By this a living body grows. 2. Alteration-certain periodic changes, in definite order, by which they lose portions of their substance and die: partial death is the accompaniment of all life. 66 Anatomy of Vertebrates," Introd. p. xxi.: Owen. 2 Ibid. Introd. p. xxxvi. 3 “First Principles,” pp. 443, 444: Herbert Spencer. Types of Animal Structure. 215 3. Reproduction-Living bodies have, directly or indirectly, the power of giving origin to germs which develop into the parent's likeness. 4. Motion-Every living body is the seat of energy, by which the inertia of matter is overcome; is master of physical forces; and this power in man, wielded by intelligence, brings the dead matter of the universe into obedience to his will. 5. The life of all living beings seems to reside in a substance termed "protoplasm," or "bioplasm," differentiated more or less, which bears to it about the same relation that a conductor does to the electric current; but in no way possesses life as an inherent property. 6. The great majority of all living beings are organisedthat is, possess organs or parts which perform functions. Do not live because they are organised, but are organised and have structure because they live. There is something in the nature and action of vital energies different from anything observed in physical: it is not organism which gives life, but life which makes organism. There are six leading characteristics of life, and six different types of animal structure. At first sight we suppose that every kind of animal has its own plan; we do not imagine that a lobster and a butterfly are built upon the same type, yet they really are: all known animals spring from unity; and their great and many outward differences are arranged into six kingdoms. 1. PROTOZOA (πρŵτоs, first; (wǹ, life). Are generally very minute, composed of a nearly structureless, jelly-like substance. Infusoria, rhizopods, and sponges. They are not definitely segmented, have no nervous system, no digestive apparatus—beyond, occasionally a passage in the midst of their protoplasm. The simplest, called Monera, are small living corpuscles; nothing more than shapeless, mobile, little lumps of protoplasm. Take a rhizopod: from the outside of this creature, which has no limiting membrane, numerous thread-like processes protrude. Originating from any point of the surface, any thread may contract again and disappear; or touching some fragment of nutriment, draw it, when contracting, into the general mass-thus serving as hand and mouth. This all but structureless body may join and become confluent with its fellow bodies; and, in brief, is at once all stomach, all skin, all mouth, all limb, all lung. 2. CELENTERATA (Koîλos, hollow; evrepov, intestine). Sea-anemones, corals, sea-jellies, sea-pens. They rise con- siderably above the Protozoa in organisation. body-wall composed of two principal layers, an intestinal cavity, and a mouth leading into it. They have no organs of circulation; but a rudimentary nervous system; the mouth is surrounded by tentacles arranged in a star-like manner. The common hydra is generally taken as a type of the lowest. It can live when the duties of skin and stomach have been interchanged by turning it inside out. The rudimentary nervous system is a prophecy of mental sensation, the highest known organic condition. 3. ANNULOIDA (annulus, a ring; eldos, form). Sea-urchins, star-fishes, sand-stars, some internal parasites, as the tape-worm, with some minute aquatic creatures. The digestive canal is completely shut off from the cavity of the body; there is a distinct nervous system; a system of branched water-vessels, usually communicating with the interior; the body of the adult, often "radiate," is never composed of a succession of definite rings. They are a people who had ancestors—not noble sires-but there is in them stuff that belongs to shining creatures. Their being belongs to a world-wide process rather than to individual advance. 4. ANNULOSA and Molluscoida. Animals with bodies composed of numerous segments, or rings; and nervous system, forming a knotted cord, along the lower surface of the body. Worms, leeches, crabs, lobsters, spiders, scorpions, centipedes, insects. Some are so wonderful, you might think the strings of their life were drawn from their own inside. 5. MOLLUSCA (mollis, soft). Shell-fish, snails, cuttle-fish, nautilus. Soft bodies, hard shells; no distinct segmentation of the body; and a nervous system of scattered masses. They are typical of that which will not go up unless you hold it down. Never to grow into a grand presence. 6. VERTEBRATA. Animals with a vertebral column. The body composed of definite segments-each composed of two tubes: a dorsal containing the neural axis, and a ventral containing the viscera, blood-vessels, etc.-arranged longitudinally one behind the other. The Kinship of Life. 217 The main masses of the nervous system are placed dorsally. The limbs are never more than four in number. Fishes, amphibians, reptiles, birds, mammals. Here seem to be the first of all those living creatures who in the dull day can await the bright, man is the great uplooking one. To These modern classifications, with man at their head, are very simply arranged in the Divine account of the genealogical tree. Moving creatures in the water, creeping things on land, animals of length, birds, beasts, cattle, man. Marine life, first created, is represented by the earliest fossils; and in the order of creation-plant, fish, bird, mammal: one generation hands a lamp of higher life to the next. mark off the groups simply as beasts, birds, fishes, creeping things, is to make their differences of appearance, modes of life, and relative importance, conspicuous. Creative energy ordained natural law, with power put forth diversely: plant, fish, bird, mammal, being introduced not collectively nor simultaneously, but in different days of life. The earliest possessed characters in combination; which, nowadays, we find separately developed in different groups. The kinship of all things being authoritatively arranged: the water brought forth, the earth brought forth; the vegetable had seed in itself, the animal possessed life after his kind; the kindred are arranged in five or six fundamental plans of structure. Animals of the sub-kingdoms, framed upon the same fundamental plan, form a few leading types, which are further arranged in subordinate groups. All the shell-fish, for example, are built upon a common plan—a plan representing the ideal mollusc. In the kinship is individuality, in the unity diversity; kind after its kind so constituted as to vary greatly in the progress of geological time. Every life possesses its own life, and is a mystery greater than that of the chemical elements. The primordial germs are essentially different, and tend toward the vegetable, or toward the animal, by different lines: no plant becomes animal, no coral turns star-fish, no worm grows into leech, no cockle transforms into cuttle-fish. There are organisms with vital action not more lively than that of drops of oil fusing themselves together when they meet, and they attain no higher existence: fuse millions together, yet no other animal is formed: but we know the Infinite can compass that which the finite cannot touch. |