1881 PANGENESIS AND PEEIGENESIS 99 



avoid a difficulty with which Perigenesis (as stated by 

 Hackel) is beset, viz. that atavism sometimes occurs 

 over too large a gap to be reasonably attributed to 

 what remains of the original ' stem-vibrations ' after 

 their characters have been successively modified at 

 each ' bifurcation.' But it would be tedious to enter 

 into details. Perigenesis, in my opinion, is ' more 

 simple ' than Pangenesis, only because its terms are 

 so much more general. 



P.S. — I forgot to tell you, when we were at lunch, 

 that the seed of the grafted beets is ready for sowing ; 

 also that the vine is now four feet high, and so, I 

 should think, might be grafted next spring. 



From C. Darwin, Esq., to G. J. Bomanes. 



Down : February 3, 1880. 



I will keep your diagram x for a few days, but I 

 find it very difficult now to think over new subjects, 

 so that it is not likely that I shall be able to send 

 any criticisms ; but you may rely on it that I will do 

 my best. 



I am glad you like Guthrie's book. If you care 

 to read a little book on pure instinct, get Fabre, 

 ' Souvenirs Entomologiques,' 1879. It is really admir- 

 able, and very good on the sense of direction in insects. 

 I have sent him some suggestions such as rotating 

 the insects, but I do not know whether he will try 

 them. 



Yours very sincerely, 



Charles Darwin. 



1 Diagram for a lecture on ' Mental Evolution.' 



h2 



