290 SCIENTIFIC THOUGHT. 



quently put forward and popularly accepted. It is 

 useful then to note that in the course of the second 

 half of the century we were more and more grow- 

 ing out of the cyclical and realising the meaning of 

 g. the genetic l view of things natural. We have been 



Supplanted . ...... 



by genetic taught in astronomy to inquire into the origin of our 

 solar or any similar system and the conditions of its 

 duration, to ask concerning the central heat of the sun 

 whence it came and how long it will last a question 

 unknown to Laplace, to consider the effects of tidal 

 friction, to learn that all the movements in nature are 

 irreversible as distinguished from completely reversible 

 ones, which only exist in abstraction ; and, finally, we are 

 met with the doctrine of the immortality of the germ- 

 plasma, an idea, the meaning and significance of which I 

 shall have to explain later on. All these novel theories 

 -and views combine to impress upon us the general 

 significance of the terms " genesis, evolution, develop- 

 ment," the fact that everything in and around us, in 

 spite of the seeming recurrence of smaller movements and 

 phenomena, and of the periodicity of the minuter and 

 elementary changes, is slowly, continuously, and inevit- 

 ably tending in a definite direction, which is certainly 

 not that of a cyclical recurrence. 

 9. Leaving aside for a moment these more general views, 



Geology. 



which have been clarified in the course of our century, 

 it is interesting to note how they gradually emerged in 



1 Perhaps it would be more periodic or cyclical movement of 



correct to say that we were learning things around us, that branch which 



to consider the changes within the we are pleased to call the ascending 



larger cycles, confining ourselves to or progressive branch, 

 the study of one branch only of the 



