Hence it is that there is a difference,2452 also, in the fins of fish, which have been given them to serve in place of feet, none having more than four,2453 some two2454 only, and others none.2455 It is in Lake Fucinus2456 only that there is a fish found that has eight fins2457 for swimming. Those fishes which are long and slimy, have only two at most, such, for instance, as eels and congers: others, again, have none, such as the muræna, which is also without gills.2458 All these fish2459 make their way in the sea by an undulatory motion of the body, just as serpents do on land; on dry land, also, they are able to crawl along, and hence those of this nature are more long-lived than the others. Some of the flat-fish, also, have no fins, the pastinacæ,2460 for instance—for these swim broad-wise—those, also, which are known as the “soft” fish, such as the polypi, for their feet2461 serve them in stead of fins.