life is dawn on the earth 30

life is dawn on the earth 30

"My own notions of Eozoic structure have been formed on the

examination of the Canadian specimens selected by the experienced

discrimination of Sir William Logan, as those in which there was

_least_ appearance of metamorphism; and having found in these what I

regarded as unmistakable evidence of an organic structure conformable

to the foraminiferal type, I cannot regard it as any disproof of

that conformity, either to show that the true Eozoic structure has

been frequently altered by mineral metamorphism, or to adduce the

occurrence of Ophites more or less resembling the Eozoon of the

Canadian Laurentians at various subsequent geological epochs. The

existence of any number or variety of _purely mineral_ Ophites would

not disprove the organic origin of the Canadian Eozoon--unless

it could be shown that some wonderful process of mineralization

is competent to construct not only its multiplied alternating

lamellæ of calcite and serpentine, the dendritic extensions of the

latter into the former, and the 'acicular layer' of decalcified

specimens, but (1) the _pre-existing canalization_ of the calcareous

lamellæ, (2) the _unfilled nummuline tubulation_ of the proper

wall of the chambers, and (3) the peculiar _calcarine_ relation of

the canalization and tubulation, here described and figured from

specimens in the highest state of preservation, showing the _least_

evidence of any mineral change.

 

"On the other hand, Professors King and Rowney began their studies of

Eozoic structure upon the Galway Ophite--a rock which Sir Roderick

Murchison described to me at the time as having been so much 'tumbled

about,' that he was not at all sure of its geological position, and

which exhibits such obvious evidences of mineralization, with such

an entire absence of any vestige of organic structure, that I should

never for a moment have thought of crediting it with an organic

origin, but for the general resemblance of its serpentine-grains

to those of the 'acervuline' portion of the Canadian Eozoon. They

pronounced with the most positive certainty upon the mineral origin

of the Canadian Eozoon, before they had subjected transparent

sections of it to any of that careful comparison with similar

sections of recent Foraminifera, which had been the basis of

Dr. Dawson's original determination, and of my own subsequent

confirmation, of its organic structure.

 

[Illustration:

Plate VIII.

 

_Eozoon and Chrysotile Veins, etc._

 

Fig. 1.--Portion of two laminæ and intervening serpentine,

with chrysotile vein. (_a._) Proper wall tubulated. (_b._)

Intermediate skeleton, with large canals. (_c._) Openings of

small chamberlets filled with serpentine. (_s._) Serpentine

filling chamber. (_s^1._) Vein of chrysotile, showing its

difference from the proper wall.

 

Fig. 2.--Junction of a canal and the proper wall. Lettering as in

Fig. 1.

 

Fig. 3.--Proper wall shifted by a fault, and more recent chrysotile

vein not faulted. Lettering as in Fig. 1.

 

Fig. 4.--Large and small canals filled with dolomite.

 

Fig. 5.--Abnormally thick portion of intermediate skeleton, with

large tubes and small canals filled with dolomite.]

 

 

 

 

CHAPTER VIII.

 

THE DAWN-ANIMAL AS A TEACHER IN SCIENCE.

 

 

The thoughts suggested to the philosophical naturalist by the

contemplation of the dawn of life on our planet are necessarily many

and exciting, and the subject has in it the materials for enabling the

general reader better to judge of some of the theories of the origin of

life agitated in our time. In this respect our dawn-animal has scarcely

yet had justice; and we may not be able to render this in these pages.

Let us put it into the witness-box, however, and try to elicit its

testimony as to the beginnings of life.

 

Looking down from the elevation of our physiological and mental

superiority, it is difficult to realize the exact conditions in which

life exists in creatures so simple as the Protozoa. There may perhaps

be higher intelligences that find it equally difficult to realize how

life and reason can manifest themselves in such poor houses of clay

as those we inhabit. But placing ourselves near to these creatures,

and entering as it were into sympathy with them, we can understand

something of their powers and feelings. In the first place it is plain

that they can vigorously, if roughly, exercise those mechanical,

chemical, and vegetative powers of life which are characteristic of

the animal. They can seize, swallow, digest, and assimilate food; and,

employing its albuminous parts in nourishing their tissues, can burn

away the rest in processes akin to our respiration, or reject it from

their system. Like us, they can subsist only on food which the plant

has previously produced; for in this world, from the beginning of time,

the plant has been the only organism which could use the solar light

and heat as forces to enable it to turn the dead elements of matter

into living, growing tissues, and into organic compounds capable of

nourishing the animal. Like us, the Protozoa expend the food which

they have assimilated in the production of animal force, and in doing

so cause it to be oxidized, or burnt away, and resolved again into

dead matter. It is true that we have much more complicated apparatus

for performing these functions, but it does not follow that this gives

us much real superiority, except relatively to the more difficult

conditions of our existence. The gourmand who enjoys his dinner may

have no more pleasure in the act than the Amœba which swallows a

Diatom; and for all that the man knows of the subsequent processes to

which the food is subjected, his interior might be a mass of jelly,

with extemporised vacuoles, like that of his humble fellow-animal. The

workman or the athlete has bones and muscles of vastly complicated

structure, but to him the muscular act is as simple and unconscious a

process as the sending out of a pseudopod to a Protozoon. The clay is

after all the same, and there may be as much credit to the artist in

making a simple organism with varied powers, as a more complex frame

for doing nicer work. It is a weakness of humanity to plume itself on

advantages not of its own making, and to treat its superior gifts as

if they were the result of its own endeavours. The truculent traveller

who illustrated his boast of superiority over the Indian by comparing

his rifle with the bow and arrows of the savage, was well answered by

the question, "Can you make a rifle?" and when he had to answer, "No,"

by the rejoinder, "Then I am at least better than you, for I can make

my bow and arrows." The Amœba or the Eozoon is probably no more than we

its own creator; but if it could produce itself out of vegetable matter

or out of inorganic substances, it might claim in so far a higher

place in the scale of being than we; and as it is, it can assert equal

powers of digestion, assimilation, and motion, with much less of bodily

mechanism.

 

In order that we may feel, a complicated apparatus of nerves and

brain-cells has to be constructed and set to work; but the Protozoon,

without any distinct brain, is all brain, and its sensation is simply

direct. Thus vision in these creatures is probably performed in a rough

way by any part of their transparent bodies, and taste and smell are no

doubt in the same case. Whether they have any perception of sound as

distinct from the mere vibrations ascertained by touch, we do not know.

Here also we are not far removed above the Protozoa, especially those

of us to whom touch, seeing, and hearing are mere feelings, without

thought or knowledge of the apparatus employed. We might so far as

well be Amœbas. As we rise higher we meet with more differences. Yet

it is evident that our gelatinous fellow-being can feel pain, dread

danger, desire possessions, enjoy pleasure, and in a simple unconscious

way entertain many of the appetites and passions that affect ourselves.

The wonder is that with so little of organization it can do so much.

Yet, perhaps, life can manifest itself in a broader and more intense

way where there is little organization; and a highly strung and

complex organism is not so much a necessary condition of a higher life

as a mere means of better adapting it to its present surroundings.

Those philosophies which identify the thinking mind with the material

organism, must seem outrageous blunders to an Amœba on the one hand, or

to an angel on the other, could either be enabled to understand them;

which, however, is not very probable, as they are too intimately bound

up with the mere prejudices incident to the present condition of our

humanity. In any case the Protozoa teach us how much of animal function

may be fulfilled by a very simple organism, and warn us against the

fallacy that creatures of this simple structure are necessarily nearer

to inorganic matter, and more easily developed from it than beings of

more complex mould.

 

A similar lesson is taught by the complexity of their skeletons.

We speak in a crude unscientific way of these animals accumulating

calcareous matter, and building up reefs of limestone. We must,

however, bear in mind that they are as dependent on their food for

the materials of their skeletons as we are, and that their crusts

grow in the interior of the sarcode just as our bones do within our

bodies. The provision even for nourishing the interior of the skeleton

by tubuli and canals is in principle similar to that involved in the

Haversian canals, cells, and canalicules of bone. The Amœba of course

knows neither more nor less of this than the average Englishman.

It is altogether a matter of unconscious growth. The process in

the Protozoa strikes some minds, however, as the more wonderful of

the two. It is, says an eminent modern physiologist, a matter of

"profound significance" that this "particle of jelly [the sarcode

of a Foraminifer] is capable of guiding physical forces in such a

manner as to give rise to these exquisite and almost mathematically

arranged structures." Respecting the structures themselves there is no

exaggeration in this. No arch or dome framed by human skill is more

perfect in beauty or in the realization of mechanical ideas than the

tests of s