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"No, you don't, sir," said Uncle Paul, with a soft chuckle. "None of your artfulness! You are trying to lead me on to prattle about Bony, so as to avoid my lecture upon the fresh-water polypes I have taken to-day. Get out, you transparent young scrub! In with you, and fetch down the case, and light the two candles on the parlour table. Nice innocent way of doing it.
If the coral polypes cannot live at a greater depth than 100 or 150 feet, how can they have built up the base of the reef-cone, which may be 2,000 feet, or more, below the surface of the sea? In order to get over this objection, it was at one time supposed that the reef-building polypes had settled upon the summits of a chain of submarine mountains.
G. Johnston's "British Zoophytes," p. 407, or the excellent little RESUME thereof in Dr. Landsborough's book on the same subject, is really a saddening one, as one sees how loth were, not merely dreamers like, Marsigli or Bonnet, but sound- headed men like Pallas and Linne, to give up the old sense-bound fancy, that these corals were vegetables, and their polypes some sort of living flowers.
Halve, or quarter, this estimate if you will, in order to be certain of erring upon the right side, and still there remains a prodigious period during which the ancestors of the existing coral polypes have been undisturbedly at work; and during which, therefore, the climatal conditions over the coral area must have been much what they are now.
As the infant polypes of the coral may retain this free and active condition for many hours, or even days, and as a tidal or other current in the sea may easily flow at the speed of two or even more miles in an hour, it is clear that the embryo must often be transported to very considerable distances from the parent.
Having understood thus far the general nature of these polypes, which are the fabricators both of the red and white coral, let us consider a little more particularly how the skeletons of the red coral and of the white coral are formed.
The apparent exceptions to this statement as in the case of the polypes, which multiply by fissiparous generation, or by spontaneous division of their bodies into parts, each part becoming a perfect animal are only apparent. These creatures, which are low down in the scale of being, exemplify what Mr.
* Dana, Manual of Geology, p. 591. Halve, or quarter, this estimate if you will, in order to be certain of erring upon the right side, and still there remains a prodigious period during which the ancestors of existing coral polypes have been undisturbedly at work; and during which, therefore, the climatal conditions over the coral area must have been much what they are now.
Darwin, looking at these curious difficulties and having that sort of knowledge of natural phenomena in general, without which he could not have made a step towards the solution of the problem, said to himself "It is perfectly clear that the coral which forms the base of the atolls and fringing reefs could not possibly have been formed there if the level of the sea has always been exactly where it is now, for we know for certain that these polypes cannot build at a greater depth than 20 to 25 fathoms, and here we find them at 50 to 100 fathoms."
The land, as it sunk, would be gone for good and all: but the coral-reef round it would not, because the coral polypes would build up and up continually upon the skeletons of their dead parents, to get to the surface of the water, and would keep close to the top outside, however much the land sunk inside; and when the island had sunk completely beneath the sea, what would be left?
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