The earliest fish appear to have been small,
elongated, eel-like creatures, closely resembling the lampreys in
structure; but they rapidly developed in size and variety, and soon
became the ruling race in the waters of the ocean, where they maintained
their supremacy till the rise of the great secondary saurians. Even
then, in spite of the severe competition thus introduced, and still
later, in spite of the struggle for life against the huge modern
cetaceans (the true monarchs of the recent seas), the sharks continued
to hold their own as producers of gigantic forms; and at the present day
their largest types probably rank second only to the whales in the whole
range of animated nature. There seems no reason to doubt that modern
fish, as a whole, quite equal in size the piscine fauna of any previous
geological age.
It is somewhat different with the next great vertebrate group, the
amphibians, represented in our own world only by the frogs, the toads,
the newts, and the axolotls. Here we must certainly with shame confess
that the amphibians of old greatly surpassed their degenerate
descendants in our modern waters. The Japanese salamander, by far the
biggest among our existing newts, never exceeds a yard in length from
snout to tail; whereas some of the labyrinthodonts (forgive me once
more) of the Carboniferous Epoch must have reached at least seven or
eight feet from stem to stern. But the reason of this falling off is not
far to seek.
Pages:
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324