LIMIT TO NATURAL KNOWLEDGE f 37 



acquired, Haeckel, moreover, considers to be the light 

 which can alone illumine the path leading to real pro- 

 gress in Philosophy and Science. 



That there is any limit to natural knowledge 

 such as is commonly assumed, Haeckel denies, and 

 bitterly censures Professor Du Bois Raymond's 

 Essay on the subject, read at the Leipzig Meeting 

 of German Naturalists in 1873, protesting against 

 the Berlin Professor's ' Ignorabimus! 



Suppose, argues Haeckel, that our single- cell 

 amoeban ancestors of the Laurentian period could have 

 been told that their descendants of the Cambrian 

 period would become a many-cell worm, they would 

 not have believed it possible. As little would these 

 worms have believed it possible that their descendants 

 would flourish as vertebrates like the Amphioxus 

 tribe and equally little would such skull-less vertebrates 

 have believed that descendants of theirs would be in 

 time developed into animals with sktills. In like 

 manner, our Silurian proto-fish ancestors would never 

 have believed that any of their Devonian grand- 

 children would exist as Amphibia and their Triassic 

 great grandchildren as Mammifera. So would those 

 mammifera have held it impossible that in the 

 Tertiary time, certain of their great great grand- 

 children would acquire Human Form and 'at the 

 same time become so highly gifted as to be qualified 

 to pluck the precious fruit of the tree of knowledge. 

 The unanimous answer from all would have been, 

 says Haeckel : ' Immutabimur et Ignorabimus,' — 



