A horse bears even less resemblance to a turnip than to an oyster; a relationship may, nevertheless, be traced, step by step, between them, dissimilar as they are.

There is the polypus, that singular product of Nature, which, regarded in one light, performs all the functions of animal life, whilst, when regarded in another, it has the ordinary attributes of a plant; does this not clearly and distinctly mark the transition from the vegetable to the animal kingdom?
Again, certain species of worms blend the animal with the insect tribe, those which are covered with a horny substance unite them with the crustaceae.

These approach fish on the one hand, and reptiles on the other, whilst reptiles in some species become moluscs." "And what is a molusc ?" inquired Willis.
"The term _molusc_ is applied by naturalists to creatures which have no vertebrae, as for example, the cuttle fish and the oyster." "I believe _you_, Mr.Wolston; but if I had asked Ernest or Jack, they would have told me that it was a commodore or an admiral." "Reptiles, I was going to say, are connected at one end of the chain with moluscs by the slug, and at the other with fish by the eel.

From flying-fish to birds the transition is by no means abrupt.

The ostrich, whose legs are like goat's, and runs rather than flies, connects birds with quadrupeds; these again return to fish through the cetacea." "Yes, but the interval between such creatures and man is still great." "True; to connect the two would be a process replete with insurmountable difficulties, and only possible to creative power.