September 1, 1886.] 



♦ KNOWLEDGE ♦ 



327 



in width, flowed in a direction somewlieie between Fran- 

 cavilla and Randazzn, and i-eached the high road which en- 

 cLi'cles the mountain, and connects the latter town with the 

 villages Linguaglosso and Piedimonte. These villages were 

 enshrouded in a canopy of ashes, and almost total darkness 

 prevailed in them. None of the ordinary concomitants of 

 a great eruption were wanting. Bftlls of fire, or what were 

 taken for such, were hurled into the air from the new 

 craters and fissures, and, having reached a great height, they 

 burst with a loud crash. Reports like the rolling of artillery 

 were heard in the night, while night and day alike the stream 

 of lava flowed stealthily and irresistibly on until it reached 

 within a short distance of Linguaglossa. 



The terrible but magnificent eruption of the present year 

 tends to confirm the belief of geologists, that, if thcearth's in- 

 ternal fires are diminishing in intensity, the diminution takes 

 jilace very slowly. A process of change may be going on which 

 will result one day in the cessation of all subterranean move- 

 ments. But the rate at which such a process is going on is 

 so slow at present as to Ije imperceptible. We cannot point 

 to a time within the historical era, or even within that ftu- 

 wider range of duration which is covered by geological 

 records, at which the earth's internal forces were decidedly 

 superior in energy to those at present in action. Nor is this 

 to be regarded as of evil import, but altogether the reverse. 

 The work achieved by subterranean action, destructive 

 though its immediate eflects may often appear, is absolutely 

 necessary to the welfare and happiness of the human race. 

 It is to the reproductive energy of the earth's internal forces 

 that we are indebted for the existence of continents and 

 islands on which warm-blooded animals can live. " Had 

 the primeval world been constructed as it now exists," says 

 Sir John Herschel, " time enough has elapsed, and force 

 enough directed to that end has been in activity, to have 

 long ago destroj'ed every vestige of land." So that, raising 

 our thoughts from present interests to the future fortunes of 

 the human race, we may agree with Sir Charles Lyell that 

 the most promising evidence of the permanence of the pre- 

 sent order of things consists in the fact that the energy of 

 subterranean movements is always uniform, when cousicfered 

 with reference to the whole of the e;irth's globe. 



THE STORY OF CREATION. 



A PLAIS ACCOUNT OF EVOLUTION. 



Bv Edward Clodd. 



X.— EXISTING LIFE-FORMS. 

 B. Animals (continued). IV. — Anki.'LOSa. 



HE common structural feature which gives its 

 name to the numerous classes of animals, 

 comprising four-fifths of exi.sting species, 

 grouped in this sub-kingdom, is the division 

 of the body into more or less well-defined 

 rings or segments. The nervous system 

 consists of tv.'O fine cords knotted at different 

 point-; by ganglia or masses of nerve-cells, the first ])air of 

 ganglia being above the gullet, so that the cords which join 

 the second pair form a collar round it. The important part 

 which the mouth plays as the immediate channel between 

 the animal and its surroundings accounts for the develop- 

 ment of the higher organs of communication near it; the 

 anterior or front segments most completely undergo concre- 

 tion, and in this way the portion that carries the mouth, 

 the chief nervous centre or brain, and the sensory organs, 

 as eyes, ears, antennse, is formed. Hence the position of 



the head or skull, as the protecting structure around the 

 more specialised parts, is ruled by the position of the mouth 

 In the annulosa the nerves run along the belly ; the heart, 

 which is tube-sliaped, lies along the back, and the digestive 

 canal is between them. This arrangement of organs distin- 

 guishes all but the veiy lowest classes, both earth-worms 

 and wasps, leeches and crabs, centipedes and beetles, lobsters 

 and auts. But the advance in complexity of structure — in 

 other words, in division of labour — is especially shown in the 

 more elaborate arrangements for the conveyance of nutrition 

 throughout the body as compared with that exhibited 

 in the lower sub-kingdoms ; e.'j., in the moneron, food and 

 oxygen enter at any and every part ; in the amteba, with 

 its primitive skin, they are driven throughout the body 

 by means of a pulsating vacuole ; in the polyp, they are 

 brought b)" the water which flushes it within and bathes 

 it without ; in the sea-urchin and the star- fish the nutriment 

 is cai-ried by the canals in their bodies which communicate 

 direct with the water. But in the liigher annulosa the oxy- 

 gen and food are circulated by a more highly organised fluid 

 called blood, which carries them to every part and likewise 

 removes the waste and effete matter, the immediate motor 

 power by which the blood is driven through the body being 

 the heart, and the aeration of the blood — in other words, 

 the supply of oxygen and the removal of carbonic acid — 

 being effected by its passage through the respiratory organs. 

 Only the back-boned animals breathe through the mouth, 

 the lower animals breathing through pores or sacs in their 

 sides. 



The annulosa may be divided into the footless, com- 

 pri-iing worms and leeches ; and the footed, comprising 

 crabs and other Crustacea, spiders, scorpions, centipedes, and 

 all insects. The jointed organs of locomotion known as 

 limbs, and which have been developed from muscle-fibres, 

 are arranged in pairs. 



Among the lowest members of the annulosa, and with 

 which almost all the higher animals are more or less con- 

 nected in descent, are Vermes or Worms — these including 

 a number of degraded forms which live as parasites inside 

 the bodies of nearly all animals, man having his share of 

 them ; whilst among the humbler but highly organised and 

 probably somewhat degraded classes are the minute Rotifers 

 (so called from the wheel-like movements of the cilia round 

 the mouth), which can remain for 3'ears in a state of sus- 

 pended animation. 



The typical form — head, thorax or chest, and abdomen 

 or belly — of the numerous varieties of the widely diffuse<l 

 Crustacea, 01 hard-shelled class, whose three-lobed ancestors, 

 the trilobites, flourished in the seas of the Cambrian and later 

 periods, is the same, with infinite modificationsin detail, asthat 

 of the i-emaining classes, from spiders to ants and beetles. But 

 in y»«c<s these three divisions are .sharply marked, the chest, 

 to which the legs and wings are attached, and the belly, 

 being sometimes joined by a mere thread, whence the name 

 given to that class — insecta, " cut into." 



Like the rotifers, with their distinct nervous system, 

 eyes, stomach, and other special organs, insects rebuke the 

 vulgar notitm that bigness is greatness, and that wonder is 

 to be projiortioned by the size of the thing which arouses it. 

 For the infinitely small is as fully charged with mystery as 

 the infinitely great ; the movements of forces and energies 

 in both cell and cry.stal are more complex than the motions 

 of the giant bodies of the heavens ; the ultimate analysis 

 of the atom is more elu.sive than that of the mass which it 

 makes up. 



In the several states of existence, or metamorphosis, as 

 it is called, through which most insects pass — egg, grub, 

 chrysalis, imago; in the beauty and delicacy of their 

 structure, notably in the wings, more perfect for flight than 



