To Ernst Haeckel   20 January 1873

My dear Häckel

I received yr magnificent work about 10 days ago. I am fairly astonished at the amount of labour which it must have cost you. The beautiful illustrations alone wd require, I shd think, months upon months of hard work. I have read with great interest the parts which you indicated, as well as some others.¹

All that I have read is extremely rich in philosophical discussions on many points. I congratulate you heartily on the completion of this great undertaking; & no doubt it will receive full attention from those naturalists (Alas! in this country few in number) who are capable of appreciating it. You are a wonderful man, but now prove yourself a wise man by taking some rest.

your admiring friend | Charles Darwin