Then came a day when one of these huge, amiable, living smiles blundered into our net, a smile a foot wide and six feet long, and even as he lay quietly awaiting what fate brought to great catfish, he sang, both theme and accompaniment. His whole being throbbed with the continuous deep drumming as the thin, silky walls of his swim-bladder vibrated in the depths of his body. The oxygen in the air was slowly killing him, and yet his swan song was possible because of an inner atmosphere so rich in this gas that it would be unbreathable by a creature of the land. Nerve and muscle, special expanse of circling bones, swim-bladder and its tenuous gas--all these combined to produce the aquatic harmony. But as if to load this contented being with largesse of apparently useless abilities, the two widespreading fin spines--the fins which correspond to our arms--were swiveled in rough-ridged cups at what might have been shoulders, and when moved back and forth the stridulation troubled all the water, and the air, too, with the muffled, twanging, _rip_, _rip_, _rip_, _rip_. The two spines were tuned separately, the right being a full tone lower, and the backward drawing of the bow gave a higher note than its forward reach. So, alternately, at a full second tempo, the four tones rose and fell, carrying out some strange Silurian theme: a muffled cadence of undertones, which, thrilled with the mystery of their author and cause, yet merged smoothly with the cosmic orchestra of wind and ripples and distant rain.