Surely not that the connection between animals is a material one; for the same kind of relation exists between lower and higher animals of one type or one class to-day, in their structural features, in their embryological growth, and in their geographical distribution, as we trace in their order of succession in time; and therefore, if this kind of evidence proves that the later animals are the descendants of the earlier in any genealogical sense, it should also prove that the animals living in one part of the earth at present grow out of animals living in another part, and that the higher animals of one class as it exists now are developed out of the lower ones. The first of these propositions needs no refutation; and with regard to the second, all our investigations go to show that every being born into the world to-day adheres to its individual law of life, and though it passes through transient phases of growth resembling other beings of its own kind, never pauses at a lower stage of development, or passes on to a higher condition than the one it is bound to fill.

If, then, this connection is not a material one, what is it? - for that such a connection does exist throughout the Animal Kingdon, as intimate, as continuous, as complex, as any series which the development theorists have ever contended for, is not to be denied. What can it be but an intel

lectual one?

These correspondences are correspondences of thought, of a thought that is always the same, whether it is expressed in the history of the type through all time, or in the life of the individuals that represent the type at the present moment, or in the growth of the germ of every being born into that type to-day. In other words, the same thought that spans the whole succession of geological ages controls the structural relations of all living beings as well as their distribution over the surface of the earth, and is repeated within the narrow compass of the smallest egg in which any being begins its growth.

CHAPTER VII.

ANALOGOUS TYPES.

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 and Analogous 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, and 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.

Cuvier has already alluded to this, when he speaks of subordination of characters, distinguishing between those controlling the whole organization and those that play only a secondary part in 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 Linnæus. Compare, for example, the Serpents among the Scaly Reptiles with the Cæcilians 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