148 THE EVOLUTION OF CONTINUITY 



the advanced ends of special evolutionary side-paths ; and 

 although any given one exhibits the same form of Continuity 

 as did the primitive type from which it evolved, yet the 

 organism in question has evolved the peculiar characters of 

 its " species," different from those of the primitive type. 



We cannot be so positive regarding extinct organisms 

 known to us only through fossil remains, for it is possible 

 that among them there might be some " mileposts " on 

 Evolution's main road. But the probability of this being 

 so seems small. For in the first place, as we shall see, the 

 main road has evidently run in a watery environment right 

 up to Segmental Continuity, and this entitles us to put 

 aside the fossils of land organisms whose Continuity is 

 lower than segmental ; while marine fossils of Continuity 

 lower than segmental are strikingly similar to organisms 

 existing at the present time, and there is reason to believe 

 that most if not all were highly evolved members of fixed 

 species at the ends of evolutionary side-paths. In our 

 opinion the same is probably the case as regards extinct 

 organisms of segmental Continuity, whether these enjoyed 

 an aqueous or terrestrial environment. 



The " testimony of the rocks " does not offer us the key 

 to the problem of living Evolution. But the present-day 

 living world in its successive types of Continuity offers us a 

 story the headings of whose chapters are distinctly legible. 

 The geological record is at the best most imperfect, and 

 although one could classify in an ascending scale of Continuity 

 the fossils which have been discovered, one could only 

 do so through a study of existing types. The key is offered 

 by Life itself, and not by its past traces. 



We have no exact knowledge of the state of the world 

 when Life first appeared, or of the real manner of the world's 

 evolution to a solid planetary condition, but there can be 

 little doubt that the latter process has been essentially one 

 of the Intensification of Continuity. This is not only 

 consistent with our own theory but also with what is called 

 the " nebular hypothesis " of the earth's origin. For this 

 hypothesis supposes that in inconceivably remote times 

 diffuse nebulae, or gaseous clouds, became heavenly bodies 

 by a process of condensation ; that our sun represents the 



