To come back to Aristotle and his fishes, let us glance at one little point more. The reproduction of the eel is an ancient puzzle, which has found its full solution only in our own day. While the salmon, for instance, comes up the river to breed and goes down again to the sea, the eel goes down to the ocean to spawn, and the old eels come back no more but perish in the great waters. The eel's egg develops into a little flattened, transparent fish, altogether different in outward appearance from an eel, which turns afterwards into a young eel or 'elver'; and Professor Grassi, who had a big share in elucidating the whole matter, tells us the curious fact that he found the Sicilian fishermen well acquainted with the little transparent larva (the _Leptocephalus_ of modern naturalists), that they knew well what it was, and that they had a name for it--_Casentula_. Now Aristotle, in a passage which I think has been much misunderstood (and which we must admit to be in part erroneous), tells us that the eel develops from what he calls γης εντερα {gês entera}, a word which we translate, literally, the 'guts of the earth', and which commentators interpret as 'earthworms'! But in Sicilian Doric, γης εντερα {gês entera} would at once become γας εντερα {gas entera}; and between 'Gasentera' and the modern Sicilian 'Casentula' there is scarce a hairbreadth's difference. So we may be permitted to suppose that here again Aristotle was singularly and accurately informed; and that he knew by sight and name the little larva of the eel, whose discovery and identification is one of the modest triumphs of recent investigation. Aristotle's many pages on fishes are delightful reading. The anatomist may read of such recondite matters as the _placenta vitellina_ of the smooth dog-fish, whereby the viviparous embryo is nourished within the womb, after a fashion analogous to that of mammalian embryology--a phenomenon brought to light anew by Johannes Müller, and which excited him to enthusiastic admiration of Aristotle's minute and faithful anatomy. Again we may read of the periodic migration of the tunnies, of the great net or 'madrague' in which they are captured, and of the watchmen, the θυννοσκοποι {thynnoskopoi}, the 'hooers' of our ancient Cornish fishery, who give warning from tower or headland of the approaching shoal. The student may learn what manner of fish it was (the great Eagle-ray) with whose barbed fin-spine--most primitive of spear-heads--Ulysses was slain; and again, he may learn not a little about that ναρκη {narkê}, or torpedo, to which Meno compared his master Socrates, in a somewhat ambiguous compliment.