2 74 Sttidies in the Theory of Descent. 



mental phenomena, from which we may then 

 attempt to trace out the inciting causes underlying 

 this development. 



The law, or, perhaps better, the line of direc- 

 tion followed by the development, is essentially 

 the following : 



1. The development commences with a state of 

 simplicity, and advances gradually to one of com- 

 plexity. 



2. New characters first make their appearance 

 in the last stage of the ontogeny. 



3. Such characters then become gradually car- 

 ried back to the earlier ontogenetic stages, thus 

 displacing the older characters, until the latter dis- 

 appear completely. 



The first of these laws appears almost self- 

 evident. Whenever we speak of development, 

 we conceive a progression from the simple to the 

 complex. This result therefore does nothing but 

 confirm the observation, that we have actually 

 here before us a development in the true sense of 

 the word, and not simply a succession of different 

 independent conditions. 



The two following laws, on the other hand, lay 

 claim to a greater importance. They are not now 

 enunciated for the first time, but were deduced 

 some years ago by Wlirtemberger 2 from a study 



8 " Neuer Beitrag zum geologischen Beweise der Darwin'schen 

 Theorie." 1873, Nos. i and 2. [This principle, in common 

 with many others which have only been completely worked out 



