344 BOTANY [CHAP. XI 



Letter 669 if so he would deserve a Royal medal. I know it is not new ; 

 but how wonderful his account of the spermatozoa of some 

 dioecious alga or conferva, swimming and finding the minute 

 micropyle in a distinct plant, and forcing its way in ! Why, 

 these zoospores must possess some sort of organ of sense to 

 guide their locomotive powers to the small micropyle ; and 

 does not this necessarily imply something like a nervous 

 system, in the same way as complemental male cirripedes 

 have organs of sense and locomotion, and nothing else but 

 a sack of spermatozoa ? 



Letter 670 To F. Hildebrand. 



May 1 6th, 1866. 



Since writing to you before, I have read your admirable 

 memoir on Salvia} and it has interested me almost as much 

 as when I first investigated the structure of orchids. Your 

 paper illustrates several points in my Origin of Species, espe- 

 cially the transition of organs. Knowing only two or three 

 species in the genus, I had often marvelled how one cell of the 

 anther could have been transformed into the moveable plate 

 or spoon ; and how well you show the gradations. But I am 

 surprised that you did not more strongly insist on this point. 



I shall be still more surprised if you do not ultimately 

 come to the same belief with me, as shown by so many 

 beautiful contrivances, that all plants require, from some 

 unknown cause, to be occasionally fertilised by pollen from 

 a distinct individual. 



II. CORRESPONDENCE WITH FRITZ MULLER, 



18651881. 



The letters from Darwin to Miiller are given as a separate group, 

 instead of in chronological sequence with the other botanical letters, as 

 better illustrating the uninterrupted friendship and scientific comradeship 

 of the two naturalists. A short biographical note on Fritz Miiller is given 

 in Vol. I., p. 382. 



Letter 671 To F. Miiller. 



Down, Oct. i;th [1865]. 



I received about a fortnight ago your second letter on 

 climbing plants, dated August 3ist. It has greatly in- 

 terested me, and it corrects and fills up a great hiatus in 



1 Pringsheiirts Jahrbiicher, Vol. IV., 1866. 



