26o TIIK CHAIN OF LIFE. 



(i) The existence of life and organisation on the earth is not 

 eternal, or even coeval with the beginning of the physical uni- 

 verse, but may possibly date from I.aurcntian or immediately 

 prc-T.aurentian times. 



(2) The introduction of new .Sj)ecies of animals and plants 

 has been a continuous process, not necessarily in the sense of 

 derivation of one species from another, but in the higher sense 

 of the continued operation of the cause or causes which intro- 

 duced life at first. This, as already stated, I take to be the 

 true theological or Scriptural as well as scientific idea of what 

 we ordinarily and somewhat loosely term creation. 



(3) Though thus continuous, the process has not been uni- 

 form ; but periods of rapid production of species have alter- 

 nated with others in which many disappeared and few were 

 introduced. This may have been an effect of physical cycles 

 reacting on the progress of life. 



(4) Species, like individuals, have greater energy and vitality 

 ' . their younger stages, and rapidly assume all their varietal 

 <;rms, and extend themselves as widely as external circum- 

 stances will permit. Like individuals, also, they have their 

 periods of old age and decay, though the life of some species 

 has been of enormous duration in comparison with that of 

 others ; tlie difference appearing to be connected with degrees 

 of adaptation to different conditions of life. 



(5) Many allied species, constituting groups of animals and 

 plants, have made their appearance at once in various parts 

 of the earth, and these groups have o])eyed the same laws 

 with the individual and the species in culminating rapidly, and 

 then slowly diminishing, though a large group once introduced 

 has rarely disappeared altogether. 



(6) ( J roups of species, as genera and orders, do not usually 

 begin with their highest or lowest forms, but with interme- 

 diate and generalised types, and they show a capacity for both 

 elevation and degradation in their subsequent history. 



(7) The history of life presents a progress from the lower to 



