no more after the six days' work was done. His Sabbath-rest having been broken by the incoming of sin, we know from John v. 17, that He continued to work without interruption; and we may fairly conclude that progressive creation was included as a part of that unceasing work. I know not whether my readers will take the same concern as I do in this subject of the dying-out of species, but to me it possesses a very peculiar interest. Death is a mysterious event, come when and how it will; and surely the departure from existence of a species, of a type of being, that has subsisted in contemporary thousands of individuals, for thousands of years, is not less imposingly mysterious than that of the individual exemplar. We do not know with any precision what are the immediate causes of death in a species. Is there a definite limit to life imposed at first? or is this limit left, so to speak, to be determined by accidental circumstances? Perhaps both: but if the latter, what are those circumstances? Professor Owen says:--"There are characters in land animals rendering them more obnoxious to extirpating influences, which may explain why so many of the larger species of particular groups have become extinct, whilst smaller species of equal antiquity have survived. In proportion to its bulk is the difficulty of the contest which the animal has to maintain against the surrounding agencies that are ever tending to dissolve the vital bond, and subjugate the living matter to the ordinary chemical and physical forces. Any changes, therefore, in such external agencies as a species may have been originally adapted to exist in, will militate against that existence in a degree proportionate to the size which may characterise the species. If a dry season be gradually prolonged, the large mammal will suffer from the drought sooner than the small one; if such alteration of climate affect the quantity of vegetable food, the bulky herbivore will first feel the effects of stinted nourishment; if new enemies be introduced, the large and conspicuous animal will fall a prey while the smaller kinds conceal themselves and escape. Small quadrupeds, moreover, are more prolific than large ones. Those of the bulk of the mastodons, megatheria, glyptodons, and diprotodons, are uniparous. The actual presence, therefore, of small species of animals in countries where larger species of the same natural families formerly existed, is not the consequence of degeneration--of any gradual diminution of the size--of such species, but is the result of circumstances which may be illustrated by the fable of 'the Oak and the Reed;' the smaller and feebler animals have bent and accommodated themselves to changes to which the larger species have succumbed."[68]