"'Is it far from here?' he said eagerly.
"'I cannot tell you at the moment. All I know is that this fountain was built in 1810 by M. Héricourt de Thury, Engineer of Subterranean Passages. As a matter of fact, this fountain is frequented by copepodes (Cyclops Fimbriatus)...'
"'Ah! Copepodes! Are they fishes?'
"'Yes; and they present modifications of tissue and coloration peculiar to themselves. They have a beautiful red eye.'
"'What? One eye?'
"'Yes; that is why they are called cyclops. But you need not be astonished that this fish has only one eye, for the Asellus Aquaticus, which also lives in the running streams of the Catacombs, a little aquatic isopode, as its name indicates, often has no eyes at all.'
"'Impossible!' cried M. Longuet. 'How do they see?'
"'They have no need to see, since they live in darkness. Nature is perfect. She is perfect in giving eyes to those who need them; she is perfect in taking away eyes from those who do not need them.'
"M. Longuet appeared to reflect a little; then he said: 'Then, if we continued to live in the Catacombs, we should end by no longer having eyes?'
"'Evidently: we should begin by losing the use of our sight and then our sight itself. Our descendants would soon lose their eyes altogether.'