He has been less of a housekeeper than most, has harvested more wind and storm, sun and sky; abroad night and day with his leash of keen scents, bounding any game stirring, and running it down, for certain, to be spread on the dresser of his page, and served as a feast to the sound intelligences, before he has done with it. We have been accustomed to consider him the salt of things so long that they must lose their savor without his to season them. And when he goes hence, then Pan is dead, and Nature ailing throughout.
His friend sings him thus, with the advantages of his Walden to show him in Nature:—
"It is not far beyond the Village church,
After we pass the wood that skirts the road,
A Lake,—the blue-eyed Walden, that doth smile
Most tenderly upon its neighbor Pines;
And they, as if to recompense this love,
In double beauty spread their branches forth.
This Lake has tranquil loveliness and breadth,
And, of late years, has added to its charms;
For one attracted to its pleasant edge
Has built himself a little Hermitage,
Where with much piety he passes life.
"More fitting place I cannot fancy now,
For such a man to let the line run off
The mortal reel,—such patience hath the Lake,
Such gratitude and cheer is in the Pines.
But more than either lake or forest's depths
This man has in himself: a tranquil man,
With sunny sides where well the fruit is ripe,
Good front and resolute bearing to this life,
And some serener virtues, which control
This rich exterior prudence,—virtues high,
That in the principles of Things are set,
Great by their nature, and consigned to him,
Who, like a faithful Merchant, does account
To God for what he spends, and in what way.
Thrice happy art thou, Walden, in thyself!
Such purity is in thy limpid springs,—
In those green shores which do reflect in thee,
And in this man who dwells upon thy edge,
A holy man within a Hermitage.
May all good showers fall gently into thee,
May thy surrounding forests long be spared,
And may the Dweller on thy tranquil marge
There lead a life of deep tranquillity,
Pure as thy Waters, handsome as thy Shores,
And with those virtues which are like the Stars!"
METHODS OF STUDY IN NATURAL HISTORY.
VII.
I come now to an obscure part of my subject, very difficult to present in a popular form, and yet so important in the scientific investigations of our day that I cannot omit it entirely. I allude to what are called by naturalists Collateral Series or Parallel Types. These are by no means difficult to trace, because they are connected by seeming resemblances, which, though very likely to mislead and perplex the observer, yet naturally suggest the association of such groups. Let me introduce the subject with the statement of some facts.
There are in Australia numerous Mammalia, occupying the same relation and answering the same purposes as the Mammalia of other countries. Some of them are domesticated by the natives, and serve them with meat, milk, wool, as our domesticated animals serve us. Representatives of almost all types, Wolves, Foxes, Sloths, Bears, Weasels, Martens, Squirrels, Rats, etc., are found there; and yet, though all these animals resemble ours so closely that the English settlers have called many of them by the same names, there are no genuine Wolves, Foxes, Sloths, Bears, Weasels, Martens, Squirrels, or Rats in Australia. The Australian Mammalia are peculiar to the region where they are found, and are all linked together by two remarkable structural features which distinguish them from all other Mammalia and unite them under one head as the so-called Marsupials. They bring forth their young in an imperfect condition, and transfer them to a pouch, where they remain attached to the teats of the mother till their development is as far advanced as that of other Mammalia at the time of their birth; and they are further characterized by an absence of that combination of transverse fibres forming the large bridge which unites the two hemispheres of the brain in all the other members of their class. Here, then, is a series of animals parallel with ours, separated from them by anatomical features, but so united with them by form and external features that many among them have been at first associated together.
This is what Cuvier has called subordination of characters, distinguishing between characters that control the organization and those that are not essentially connected with it. The skill of the naturalist consists in detecting the difference between the two, so that he may not take the more superficial features as the basis of his classification, instead of those important ones which, though often less easily recognized, are more deeply rooted in the organization. It is a difference of the same nature as that between affinity and analogy, to which I have alluded before, when speaking of the ingrafting of certain features of one type upon animals of another type, thus producing a superficial resemblance, not truly characteristic. In the Reptiles, for instance, there are two groups,—those devoid of scales, with naked skin, laying numerous eggs, but hatching their young in an imperfect state, and the Scaly Reptiles, which lay comparatively few eggs, but whose young, when hatched, are completely developed, and undergo no subsequent metamorphosis. Yet, notwithstanding this difference in essential features of structure, and in the mode of reproduction and development, there is such an external resemblance between certain animals belonging to the two groups that they were associated together even by so eminent a naturalist as Linnaeus. Compare, for instance, the Serpents among the Scaly Reptiles with the Caecilians among the Naked Reptiles. They have the same elongated form, and are both destitute of limbs; the head in both is on a level with the body, without any contraction behind it, such as marks the neck in the higher Reptiles, and moves only by the action of the back-bone; they are singularly alike in their external features, but the young of the Serpent are hatched in a mature condition, while the young of the type to which the Caecilians belong undergo a succession of metamorphoses before attaining to a resemblance to the parent. Or compare the Lizard and the Salamander, in which the likeness is perhaps even more striking; for any inexperienced observer would mistake one for the other. Both are superior to the Serpents and Caecilians, for in them the head moves freely on the neck and they creep on short imperfect legs. But the Lizard is clothed with scales, while the body of the Salamander is naked, and the young of the former is complete when hatched, while the Tadpole born from the Salamander has a life of its own to live, with certain changes to pass through before it assumes its mature condition; during the early part of its life it is even destitute of legs, and has gills like the Fishes. Above the Lizards and Salamanders, highest in the class of Reptiles, stand two other collateral types,—the Turtles at the head of the Scaly Reptiles, the Toads and Frogs at the Lead of the Naked Reptiles. The external likeness between these two groups is perhaps less striking than between those mentioned above, on account of the large shield of the Turtle. But there are Turtles with a soft covering, and there are some Toads with a hard shield over the head and neck at least, and both groups are alike distinguished by the shortness and breadth of the body and by the greater development of the limbs as compared with the lower Reptiles. But here again there is the same essential difference in the mode of development of their young as distinguishes all the rest. The two series may thus be contrasted:—
Naked Reptiles. Toads and Frogs, Salamanders, Caecilians.