PREFACE. X1x 
in the “General Morphology,’ and in the “History of 
Creation,’ is wanting in actual proofs. The proofs are 
there. Of course those who turn their eyes away from 
them will not see them. Precisely that “exact” form of 
analytical proof which the opponents of the descent theory 
demand is to be found, by anybody who wishes to find it, 
in the “ Monograph of the Calcareous Sponges.” 
ERNST HEINRICH HAECKEL. 
Jena, June 24th, 1873. 
