Answer:
That the human race is of one distinct species. It exhibits slight variations (in color, stature, mental caliber, and so on) due to climate, environment, and so forth; but it is a species by itself, and not to be confounded with any other.
That the quadrupeds are a distinct family, also. This family exhibits variations – in color, size, food preferences, and so on; but it is a family by itself.
That the other families – the birds, the fishes, the insects, the reptiles, etc. – are more or less distinct, also. They are in the procession. They are links in the chain which stretches down from the higher animals to man at the bottom.