LINNEAN SOCIKTY OF LONDON. Xl'Vll 



For the fullest details, pigeons, rabbits, horses, fowls, culinary 

 plants, and fruits are selected, as affording at once the best evidence 

 of community of origin and the most striking instances of diversity 

 in form and structure in the domesticated races j but the chapters 

 on dogs, pigs, cattle, ducks, and miscellaneous plants are equally 

 instructive. In these same chapters the effects of selection by man, 

 methodical or unconscious, are throughout kept in view and dis- 

 cussed in relation to every class of animals or plants treated of. 

 Throughout it appears that the comparative amount of variation 

 obtained under the care of man in the several organs has depended, 

 not on any innate comparative variability of the organs, but on the 

 objects sought to be attained. 



The eleventh chapter is devoted to the very curious and compara- 

 tively novel subject of bud-variation, in relation to which very few , 

 facts have as yet been observed ; but some of these, like that of the 

 Gytisus Adami, have been so startling as to have been denied in 

 part or in toto. Such as can be well authenticated are here sub- 

 jected to a most interesting discussion. They seem to bear little 

 upon the general question of origin by selection, but much more 

 upon the hypothesis brought forward in the second volume, to which 

 I shall presently allude. 



In the second volume I was much struck with the admirable 

 chapters on crossing (XV. to XIX.), as deserving of special study. 

 A methodical review of the present state of our knowledge of a sub- 

 ject which has been so much advanced by experiments and obser- 

 vations provoked by Mr. Darwin's first work, is accompanied by the 

 exposition of the various effects of the complicated phenomena of 

 crossing and interbreeding in provoking variation or in maintaining 

 the stability of species, in improving or deteriorating races, accord- 

 ing to conditions more or less known to us. 



Two chapters are devoted to a general review of methodical or 

 unconscious selection by man as well as of natural selection on 

 domesticated species, as deducible from the facts detailed in the first 

 volume, accompanied by historical sketches of changes known to 

 have been effected by these means. 



The fact of variability being established, an investigation into the 

 very obscure subject of the causes of variability, and the endeavour 

 to trace out the laws of variation, necessarily followed. Few and 

 vague as are the data from which we can judge of those causes, such 

 as Mr. Darwin has been able to collect lead him to conclude that 

 the variability of organic beings under domestication results from 

 LINN. PRoc. — Session 1867-68. h 



