488 THE RESTORATION OF EXTINCT ANIMALS. 



living to-day in order to properly interpret the bones of those that 

 lived a million years ago; not only that, it is equally essential to 

 have more than a casual acquaintance with their external appearance, 

 for, while there is nothing in the bones to tell how an animal is or 

 was covered, there are certain general i-ules for telling what the prol)- 

 al)ilities ai'e. 



A l)ir(l. for example, would certainly be clothed in feathers, for 

 these ai'c the exdusixc ])r()perty of hii'ds; no other creature possesses 

 feathei's. no bird is w itliout tiieni, although they may be so modified that 

 at first sight theii- identity might be called in (juestion. Reptiles and 

 mannnals may go (piite naked or cover themselves with a defensive 

 armor of bony plates or horny scales, but under the blaze of the 

 tropical sun or in the chill waters of arctic seas birds wear feathers 

 and feathers oidy. (loing a little further, we might l)e pretty sure 

 that the feathers of a waterfowl would b(> thick and close; those of 

 strictly terrestrial birds, such as the ostrich and otlicn- flightless forms, 

 lax and long. These as general propositions. Of course in special 

 cases one might easily come to grief, as in dealing with birds like 

 penguins, which are particularly adapted for an aquatic life and have 

 the feathers highly modified. These birds depend upon their fat and 

 not on their feathers for warmth, and thes(> have become a sort of 

 cross between scales and hairs. Hair and fur belong to mammals 

 only, although these crtnitures show nuich variety in their outer cover- 

 ing. The thoroughly marine whales have discarded furs and adopted 

 a smooth and slippery skin,' well adapted to movement through the 

 water, relying for warmth on a thick undershirt of blubber. The 

 earless seals, that pass much of their time on the ice, have just enough 

 hair to keep them from absolute contact with it, warmth again being 

 provided for by l)lubber. The fur seals, which for several months in 

 the year dwell largely on land, have a coat of fur and hair, although 

 warmth is mostly furnished, or rather kept in, by fat. 



No reptile, therefore, would be covered with feathers; neither, judg- 

 ing from those we know to-day. would they be clad in fur or hair; but 

 such coverings being barred out, there remain a great variety of plates 

 and scales to choose from. Folds and frills, crests and dewlaps, like 

 beauty, are but skin deep, and, being thus superficial, ordinarily leave 

 no trace of their former presence, and in respect to them the recon- 

 structor must trust to his imagination with the law of probabilities as 

 a checkrein to his fancy. This law would tell us that such ornaments 



1 The reader is warned that this is a mere figure of speech, for, of course, the proc- 

 ess of adaptation to surroundings is passive, not active, although tliere is a most 

 unfortunate tendency among writers on evolution, and particularly on mimicry, to 

 speak of it as active. The writer believes that no animal in the first stages of 

 mimicry consciously mimics or endeavors to resemble another animal or any part of 

 its surroundings, but a habit at first accidental may in time become more or less 

 conscious. 



