296 



SCIENTIFIC THOUGHT. 



Embryol- 

 ogy. 



to draw indefinitely on the great bank of time/ just as in 

 former ages they had been quickly brought to book by 

 existing prejudices.^ 



Wliilst these contributions to the genetic view of 

 nature on the large scale were being independently 

 worked out, the sciences which deal with the minute 

 and hidden phenomena of organic growth had made great 

 progress in the same direction. Here a definite scheme 

 of development was quite evident to the most casual 

 observer. In these sciences indeed we have to do with 

 what is called in the German language " the history of 

 development " 'par excellence, a term which is inadequately 

 rendered by " Embryology " in French and English. For 

 it is an error which has frequently and for long periods 

 obscured the correcter view to assume that the chang;es 

 and processes which characterise the development of 

 embryonic or germ life are essentially different from 

 those which exist in the larger and more complex adult 

 organism. The abohtion of the fundamental distinction 

 between the processes of embryonic and of adult or f ull- 



1 Lyell, vol. iii. p. 358 : " Cou- 

 fiiied notions in regard to the 

 quantitj' of past time have tended 

 more than any other prepossessions 

 to retard the progress of geology, 

 . . . and until we habituate our- 

 selves to contemplate the possibility 

 of an indefinite lapse of ages having 

 been comprised within each of the 

 more modern periods of the earth's 

 history, we shall be in danger of 

 forming most erroneous views in 

 geology." 



- One of the first to attack the 

 uniformitarian doctrine in geology 

 and to applj' the principles of 

 modern physical science to geolog- 



ical and cosmical questions in this 

 country was Lord Kelvin. His 

 influence belongs, however, mainly 

 to the post-Darwinian period, and 

 begins with his celebrated memoir 

 ' On the Secular Cooling of the 

 Earth' (Edin. Trans., 1862, re- 

 printed in the 3rd vol. of ' Math, 

 and Phys. Papers,' p. 295). See 

 also the 2nd vol. of his ' Popular 

 Lectures and Addresses.' Accord- 

 ing to the introductory statement 

 in the former paper his doubts 

 regarding the uniformitarian teach- 

 ing began as early as 1844. I shall 

 refer to these speculations at the 

 end of this chapter. 



