To him[244] by right belongs the distinction, which (except incidentally in Mr. Lones’ work[245]) I have so far failed to find attributed to him, of being the first writer to note, certainly the first to point out, that its scales make possible a shrewd, in the case of the murex an exact, computation of the age of a fish.
If from lack of the microscope he did not in all particulars antedate, he certainly blazed the trail for the discovery of scale-reading at the close of the eighteenth century by the Dutch microscopist van Leeuwenhoek[246] and its rediscovery as regards the carp in 1899 by Hoffbauer,[247] the Gadidæ and Pleuronectidæ in 1900-03 by J. Stuart Thomson,[248] and the Salmonidæ about 1904 by H. W. Johnston and others.[249]
He tells us in The Natural History, I. 1, that “what the feather is in a bird, the scale is in a fish”; in III. 11,[250] that “the scales of fish become harder and thicker, and in those which are wasting or aging, become still harder”; in VIII. 30, that “the old fish are distinguishable by the size” (note this!) “and the hardness of their scales.”[251]
He then buttresses this discovery of annual growth of scale by another fact resulting from his observation that “the Murex lives for about six years, and the yearly increase is indicated by a distinct interval in the spiral convolution of the shell,”[252] or as Bohn renders the words, “its annual increase is seen in the divisions on the helix of its shell.”
In Leeuwenhoek we read that, in the examination by a rough self-made microscope of the scales of a large tame carp, he counted the component scale-layers lying one above the other, “as if glued together,” and found without exception that a new layer larger than the one of the preceding year is added. The carp, accidentally killed when forty years old, possessed forty such layers in each scale. He adds pathetically—anticipating perhaps Lytton’s—
“A Reformer, a creed by posterity learnt A century after its author is burnt”—
that “many people accused me of telling lies on the matter!”[253]
One cannot help being struck with acute astonishment that for over the 2000 years between Aristotle and Leeuwenhoek we obtain, with the exception[254] of nine words in Pliny (IX. 33), Senectutis indicium squamarum duritia, quæ non sunt omnibus similes, cribbed and condensed, as was often his wont, from Aristotle, little, if any, addition to our knowledge of scale-reading.
The ancient authors either ignore or are ignorant of it. Nowhere, not even in that close observer Oppian, that omnivorous reader Athenæus, that pleasant purloiner Ælian, do we read a single line on the subject. But our astonishment, even if we allow for absence of microscope, grows acuter, when we are met in the three most important Ichthyologists before the eighteenth century, Belon, Salviani, and Rondolet, with the same silence.
And this fate of silence apparently prevails even after Leeuwenhoek’s book; his discovery seems to have been lost or remained dormant in his pages till a score of years ago.