THE WONDERS OF LIFE 



step by step from the lower. To this physiological 

 scale corresponds exactly the morphological gradation 

 revealed by the comparative anatomy of the brain. 

 The most interesting and important part of this is that 

 which relates to the highest developed class — the 

 mammals; within this class we find the same ever- 

 advancing gradation. At its summit are the primates 

 (man, the apes, and the half -apes), then the carnivora, a 

 part of the ungulates, and the other placentals. A wide 

 interval seems to separate these intelligent mammals 

 from the lower placentals, the marsupials and mono- 

 tremes. We do not find in the latter the high quantita- 

 tive and qualitative development of the phronema which 

 we have in the former; yet we find every intermediate 

 stage between the two. The gradual development of the 

 cerebrum and its chief part — the phronema — took place 

 during the Tertiary period, the duration of which is 

 estimated by many recent geologists at from twelve to 

 fifteen (at the least three to five) million years. 



As I have gone somewhat fully, in chapters vi.-ix. of 

 the Riddle, into the chief results of the modern study of 

 the brain and its radical importance for psychology and 

 the theory of knowledge, I need only refer the reader 

 thereto. There is just one point I may touch here, as 

 it has been attacked with particular vehemence by my 

 critics. I had made several allusions to the works of 

 the distinguished English zoologist, Romanes, who had 

 made a careful comparative study of mental develop- 

 ment in the animal and man, and had continued the 

 work of Darwin. Romanes partly retracted his monis- 

 tic convictions shortly before his death, and adopted 

 mystic reUgious views. As this conversion was only 

 known at first through one of his friends, a zealous Eng- 

 lish theologian [Dr. Gore], it was natural to retain a 

 certain reserve. However, it turned out that there had 

 really been in this case (just as in the case of the aged 



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