example, are closely allied by similarity of construction; but the former changes little, the latter presents three forms before attaining the mature beauty of prawn life. The Death'sHead Moth possesses the power of squeaking.

The caterpillars, Attacus acropia, from Louisiana, at first nearly black, decorated with hairs, look like little hedgehogs. Moulting, they become grey-green or russet in colour, all the tubercles or spines brilliantly black. Again moulting, they are bright green, with five rows of black spots; two magnificent tubercles of a carmine colour are on the second and third segments, and two of light yellow are on the dorsal part of every other segment. At a third moult, the body is azure blue on the back, with black spots on the sides and head; the tubercles form two rows on the back, are red and much enlarged; the other tubercles have a single spine upon them. At the last moult, the caterpillar is of a pale green colour, all the lateral tubercles are light green, the red tubercles have taken an orange tint and have only one spine. Then it forms a double cocoon-the outside hard and like parchment in texture, the interior silky-where it is transformed into the moth.1

Some caterpillars fast for nine months; larvæ of the next kind eat and grow big; there is more in the philosophy of this than we know: metamorphosis is not determined by simple physical influences, it often refers back to ancestral peculiarities. The processional caterpillars go forth under a leader to their food, and return in the same array, yet nothing distinguishes the leader from the others. Caterpillars, much alike, become moths which present marked distinctions; and moths, which resemble one another, proceed from very dissimilar caterpillars. Metamorphoses are generally an advance, but the female winter moth, Climata brumata, and Psyche, positively retrograde; the male advances, has wings, but the female is without even the moving power of the caterpillar : whereas, the female Nemoura are perfectly developed as winged flies; but the wings of the males are rudimentary and short. Of a moth, the Psyche helix, we only know the female; the virgin females lay eggs which become perfect females. In 1 "Transformations of Insects," p. 111: Dr Duncan.

like manner, isolated female wasps give birth to eggs which turn to females, no males; which again produce their like.1

The Hymenoptera, most highly endowed of all insects, are in an early stage most helpless; the larvæ of ants, for example, must have the food put into their mouths. The instinct, or sense of hearing or of smell, that enables the parasitic Hymenoptera to discover a larva inside a fruit, or within a branch or trunk of a tree, and perfectly out of sight, makes us wonder. Some non-carnivorous insects hunt and catch prey for their carnivorous young; then stupify the prey so that it may remain alive, even for months, but in helpless state, for the young to feed on. All known Beetles lay eggs, but in 1864 Schiödte discovered that the Staphylinidæ produced living larvæ. All the Myriapods respire by agency of tracheæ, but Sir John Lubbock has described a curious little myriapod, Pauropus, which he says has a look of cheerful intelligence, no trachea, and respires, he supposes, through the skin. All these varieties, of which natural uniformity is the theatre for display, are indications of a mysterious energy working in particular ways, adjusting inner and outer relations; and, however elevated and complicated the result, it is wrought by means of the simplest elements, and generally by insensible degrees.

The smallest amount of intelligence requires perfect organization but mechanical appliances, implements, tools, necessary to produce good work, do not convey intelligence, though they may be called its mechanical basis. Nature seems to have a purpose in everything, and does work as knowing how to do it, though the purposeless or "silent members" in animal frames are hard to account for. Some animals have teeth, never meant to eat with; there are rudiments of toes in a horse, and teats in male animals, utterly useless. Are we thence to infer that eyes are not meant to see with; nor feet to walk with; nor teeth to eat with; nor was "a duck expressly intended to be a duck with a web-foot, that it might pleasantly move on the water; but its forefathers and mothers a long way back began, under pressing circumstances, to get a duckish disposition; and by dint of endeavour for ages to "Transformations of Insects," pp. 158, 238: Dr Duncan.

try their chance of paddling themselves about on the pools
of a puddly world, their efforts were at length rewarded, and
resulted in a complete success—so remarkable indeed, at last,
that a generation sprang from them thoroughly equipped for
the waters with web-feet, oily back, boat-shaped bodies,
spoony bills, and bowels to correspond with mudworms and
duckweed." 1
Surely it is time to lay aside notions so
grotesque, and to live, as did Newton and Boyle, in the con-
ception that

"God dwells within, and moves the world and moulds,
Himself and Nature in one form enfolds."

GOETHE.

If not able to assign a purpose for purposeless structures we are less able to account for them as a natural selection: they would be an unnatural selection. It is inconceivable that any creature could or would voluntarily grow them; nor can we credit that any brute is able to make an intelligent attempt to become intelligent. It is incredible that nature would put swiftness from the feet, fangs from the mouth, claws from the paws, and cast aside the acute sense of smell, in order to advance in life; or that any intelligent creature would divest itself of those advantages. As for time and space they are not structural causes, and could never enable any brute to generate a progeny that would submit to conditions of moral responsibility. If, however, we consider that "silent members" were of use in the past, or are for use in the future; that there is in nature an agency of use and disuse; light begins to shine in the darkness. Rudimentary organs will then show somewhat of the stages by which old forms die out and new forms come in: by modifications acting through generations of ancestral organisms. If not, there is another explanation:-The finished and complicated parts of our most wonderful machinery are all found typified in simpler shape, and narrower use in smaller or in primitive engines so the imperfect organs of lower animals become perfect in higher creatures. In like manner, the human mind is a real though faint emblem of the Wisdom of which

1 "The First Man and His Place in Creation," p. 36: Geo. Moore, M.D.

all natural phenomena are manifestations. We have a sketch, in ourselves, of the detail and plan which are worked up into the universal fabric: the lower anticipating the higher, and the higher fulfilling that anticipation.

The battle of life, therefore, through all time and in every field represents an unseen influence but visible in effect, taking away the feeble from an unequal contest, laying aside the lame if they cannot be made to walk, and carrying off the blind if they cannot be made to see; that the strong, the swift, the clear-sighted, may attain perfection. Butler's comparison may be true, that waste of seeds, like waste of souls, is a condition of psychic and organic progress; an analogue of selection carried out in the spiritual world. "Life is not a bully who swaggers out into the open universe, upsetting the laws of energy in all directions, but rather a consummate strategist, who, sitting in his secret chamber over his wires, directs the movements of a great army,"1 and leads his forces to possess the worlds.

We pass now from Varieties in Life to the Manifold Changes of Inorganic Matter.

Chemistry is the science of experimental surprises. The most inert substances often producing, by combination, compounds of the strongest energy; the tasteless becoming intensely sour, sweet, or bitter; water, that quenches fire, containing the elements of fire; and the things which give and gladden life turning into demons of destruction. Many mineral, vegetable, and animal poisons, having apparently little in common, produce the same effect on the muscles as heat. The chemical union of different kinds of atoms, in the definite proportions of whole numbers, entirely changes their characters and properties. Two different liquids often condense into a solid; and the result of the chemical combination of two various gases or vapours, in quantitive proportions, may be solid, liquid, or aeriform. The ingredients of that acrid, dangerous, corrosive liquid, aquafortis, in different proportions, are constituents of the summer breeze. Another affinity of our atmosphere produces "laughing gas." More surprising, there are compound substances absolutely identi

1 "The Unseen Universe."

cal in the number and relative proportions of elements which in colour, odour, taste, are wholly unlike. The same substance will act as an acid in one combination, and as a base in another. Indeed, chemical laws seem imperfectly stated cases of some more general law of combination.

A piece of sugar falls into water, and sinks by law of gravity; but in a little while, it is found to have ascended and sweetened the whole. The same happens with salt, alum, and various other substances; yet, oil poured on the water will not diffuse itself through the mass; and gases of different densities put into a vessel will not, according to gravity, take different levels; but, by the law of diffusion, commingle.

Every different body requires a different quantity of heat to produce in it the same change of temperature; and the volume of most substances increases continuously as the temperature rises; but there is at least one exception among solid bodies-Iodide of Silver. The three principal states in which matter is found are the solid, the liquid, the gaseous; but most substances, probably all, are capable of existing in every one of these states; and the solid, passing into the liquid, is actually hotter than the liquid-the surplus heat is called latent. There is generally a change of bulk in the act of fusion; some expand, some diminish, we know not why. Ice dissolves into water of less bulk, but most substances enlarge. It requires more heat at high than low temperature to warm liquid one degree. Most liquids contract with cold, but water expands from 39° F. to 32° F., and then contracts. A glacier moves slowly on like a viscous body, an india-rubber band suddenly stretched out becomes warmer, if you pull out a steel spring it becomes colder. The conversion of liquid into vapour requires an amount of latent heat which is generally much greater than the latent heat of fusion of the same substance, and when a gas is near its point of condensation, its density increases more rapidly than the pressure. When it is at the point of condensation, the slightest increase of pressure condenses the whole into liquid, which seems contrary to the law-" the pressure of a gas is proportional to its density." In the liquid form the density increases very slowly