344 LIFE OF PROFESSOR HUXLEY CHAP. XVII 



in in destroying fertility. But the sterility which must 

 be obtained by the selective breeder in order to convert 

 his morphological species into physiological species 

 such as we have in nature must be quite irrespective 

 of breeding in and in. 



There is no question of breeding in and in between a 

 horse and an ass, and yet their produce is usually a sterile 

 hybrid. 



So if Carrier and Tumbler, e.g., were physiological 

 species equivalent to Horse and Ass, their progeny ought 

 to be sterile or semi -sterile. So far as experience has 

 gone, on the contrary, it is perfectly fertile as fertile 

 as the progeny of Carrier and Carrier or Tumbler and 

 Tumbler. 



From the first time that I wrote about Darwin's book 

 in the Times and in the Westminster until now, it has 

 been obvious to me that this is the weak point of Darwin's 

 doctrine. He has shown that selective breeding is a vera 

 causa for morphological species ; he has not yet shown it 

 a vera causa for physiological species. 



But I entertain little doubt that a carefully devised 

 system of experimentation would produce physiological 

 species by selection only the feat has not been performed 

 yet 



I hope you received a copy of Man's Place in Nature, 

 which I desired should be sent to you long ago. Don't 

 suppose I ever expect an acknowledgment of a book it 

 is one of the greatest nuisances in the world to have that 

 to do, and I never do it but as you mentioned the 

 Lectures and not the other, I thought it might not have 

 reached you. If it has not, pray let me know and a copy 

 shall be forwarded, as I want you very much to read 

 Essay No. 2. 



I have a great respect for all the old bottles, and if 

 the new wine can be got to go into them and not burst 

 them I shall be very glad I confess I do not see my 

 way to it ; on the contrary, the longer I live and the 



