MACKIE — FIRST TRACES OF THE SUCCESSION OF LIFE. 3^3 



The first glance at the familiar objects aronnd us assures us that 

 all li\^ing things have not the same values of structure or the like 

 capabilities of life. We perceive at once that some are of far lower 

 grades both of intelligence and action ; that in point of fact there is 

 a scale of development of the social rank both of animals and 

 vegetables. These conditions are so apparent and so well known 

 that it would be useless to dwell upon them. We proceed therefore 

 at once to mark out the divisions of the animal and vegetable king- 

 doms, and the particular characters by which each is indicated, 

 premising that, as in the inorganic world there is no decided 

 natural line of division between one rock-mass and the others, one 

 stratum and another, in the succession of formation, and that what 

 appears a break in the series in one place is filled up by some 

 deposit in another, so in the organic world each genus, family, and 

 order are so linked by modifications and divergences to others, that 

 the actual lines of division are essentially arbitrary, and especially in 

 the more minute scientific and natural divisions, as between species, 

 genera, and families ; the higher gToups appearing, however, as far 

 as our present knowledge extends, to be merely linked together by 

 similitudes, or by the devarication of one type into an apparent re- 

 semblance to another rather than by any natural afiinities between 

 them. 



We now present in Table I. the primary constituent members of 

 these great divisions as nearly as may be in the ascending order of 

 their organic development and ranl^, thus placing Man, the highest, 

 at the top, and the E/hizopods — Protozoans at the base of the series. 

 The groups of animal-forms must not be altogether regarded as in- 

 dicating a progressive increased rank of organization ; many of 

 them are of equal value with each other, and the exact position of 

 others has not been thoroughly determined. Moreover, no system 

 of classification of organic forms, whether vegetable or animal, can 

 be as yet regarded as perfect ; the best can only be considered artifi- 

 cial and provisional, requiring many modifications and improve- 

 ments ; hence the student or general reader must not therefore 

 be dismayed at the difierence of position assig-ned by difierent 

 naturalists to particular organisms, nor think that naturalists are 

 ignorantly difiering from each other in their ideas. I^or must they 



