38 SPREAD OF EVOLUTION. [1865. 



observations on Classification and Embryology seem to me 

 very good and original. They show what a wonderful field 

 there is for enquiry on the development of Crustacea, and 

 nothing has convinced me so plainly what admirable results 

 we shall arrive at in Natural History in the course of a few 

 years. What a marvellous range of structure the Crustacea 

 present, and how well adapted they are for your enquiry ! 

 Until reading your book I knew nothing of the Rhizocephala ; 

 pray look at my account and figures of Anelasma, for it seems 

 to me that this latter cirripede is a beautiful connecting link 

 with the Rhizocephala. 



If ever you have any opportunity, as you are so skilful a 

 dissector, I much wish that you would look to the orifice at 

 the base of the first pair of cirrhi in cirripedes, and at the 

 curious organ in it, and discover what its nature is ; I sup- 

 pose I was quite in error, yet I cannot feel fully satisfied at 

 Krohn's * observations. Also if you ever find any species of 

 Scalpellum, pray look for complemental males ; a German 

 author has recently doubted my observations, for no reason 

 except that the facts appeared to him so strange. 



Permit me again to thank you cordially for the pleasure 

 which I have derived from your work, and to express my 

 sincere admiration for your valuable researches. 



Believe me, dear Sir, with sincere respect, 



Yours very faithfully, 

 Ch. Darwin. 



P.S. — I do not know whether you care at all about plants, 

 but if so, I should much like to send you my little work on 

 the ' Fertilization of Orchids,' and I think I have a German 

 copy. 



Could you spare me a photograph of yourself? I should 

 much like to possess one. 



* See Vol. II. p. 345, Vol. III. p. 2. 



