rest of the organization, whether they be called pectoral and ventral fins, or legs, or wings and legs, or arms and legs. Notwithstanding the rudimentary condition of these limbs in some Vertebrates and their difference of external appearance in the different groups, they are all built of the same structural elements. These are the typical characters of the whole branch, and exist in all its representatives. What now are the different modes of expressing this structural plan that lead us to associate certain Vertebrates together in distinct classes? Beginning with the lowest class,--the Fishes are cold-blooded, they breathe through gills, and they are egg-laying; in other words, though they have the same general structure as the other Vertebrates, they have a special mode of circulation, respiration, and reproduction. The Reptiles are also cold-blooded, though their system of circulation is somewhat more complicated than that of the Fishes; they breathe through lungs, though part of them retain their gills through life; and they lay eggs, but larger and fewer ones than the Fishes, diminishing in number in proportion to their own higher or lower position in their class. They also bestow greater care upon their offspring than most of the Fishes. The Birds are warm-blooded and air-breathing, having a double circulation; they are egg-laying like the two other classes, but their eggs are comparatively few in number, and the young are hatched by the mother and fed by the parent birds till they can provide for themselves. The Mammalia are also warm-blooded and breathe through lungs; but they differ from all other Vertebrates in their mode of reproduction, bringing forth living young which they nurse with milk. Even in the lowest members of this highest group of the Vertebrates, at the head of which stands Man himself, looking heavenward it is true, but nevertheless rooted deeply in the Animal Kingdom, we have the dawning of those family relations, those intimate ties between parents and children, on which the whole social organization of the human race is based. Man is the crowning work of God on earth; but though so nobly endowed, we must not forget that we are the lofty children of a race whose lowest forms lie prostrate within the water, having no higher aspiration than the desire for food; and we cannot understand the possible degradation and moral wretchedness of Man, without knowing that his physical nature is rooted in all the material characteristics that belong to his type and link him even with the Fish. The moral and intellectual gifts that distinguish him from them are his to use or to abuse; he may, if he will, abjure his better nature and be _Vertebrate_ more than Man. He may sink as low as the lowest of his type, or he may rise to a spiritual height that will make that which distinguishes him from the rest far more the controlling element of his being than that which unites him with them. LOVE AND SKATES. IN TWO PARTS. PART II.