. Outlines of zoology. ldest bird — Archaopteryx — is in many ways aconnecting link between the two classes; and the develop-ment of some Birds reveals many remarkable resemblanceswith that of Reptiles,—therefore, with the strength of thegeneral argument for evolution to corroborate us, weconclude that Birds evolved from a Reptile stock. It is likely, then, that Birds arose from an ancient Saurianstock, but by what steps and under what impulses we donot know. To some it seems enough to say that theevolution was accomplished gradually in the course ofnatural selection by the fostering of fit va
. Outlines of zoology. ldest bird — Archaopteryx — is in many ways aconnecting link between the two classes; and the develop-ment of some Birds reveals many remarkable resemblanceswith that of Reptiles,—therefore, with the strength of thegeneral argument for evolution to corroborate us, weconclude that Birds evolved from a Reptile stock. It is likely, then, that Birds arose from an ancient Saurianstock, but by what steps and under what impulses we donot know. To some it seems enough to say that theevolution was accomplished gradually in the course ofnatural selection by the fostering of fit variations and theelimination of the disadvantageous; to others it seems thatthe incipient birds were ^^fevered representatives of reptiles,progressing in the direction of greater and greater con-stitutional activity; but both these suggestions leavemuch in the dark, leave us still to wonder how theslow, coldblooded, scaly beast ever became transformedinto the quick, hot-blooded, feathered bird, the joy Fig. -Fore-limb and shoulder-girdle (I.) andhind-limb (II.) of rabbit. Scapula ; A., acromion ; Jlf.^ metacromion process ; ^.,-humerus;O., olecranon process; I/., ulna; li., radius; C., carpals; MC,metacarpals; Z>,, five digits; J^., femur; P., patella; F/., fibula;T., tibia; OC, os calcis; AS.^ astragalus; VT., distal tarsals; metatarsals; four digits. CHAPTER XXVI Class MAMMALIA I. Prototheria; 2. Metatheria; 3. Eutheria Birds and Mammals have evolved along very differentlines, Birds possessing the air and Mammals the earth, andit is difficult to say that either class is the higher. Butapart from the fact, which prejudices us, that man himselfis zoologically included among Mammals, this class issuperior to Birds in two ways—^m brain development, andin the relation between mother and offspring. In mostMammals there is a prolonged organic connection betweenthe mother and the unborn young, which may have been,as Robert Chambers suggested
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
