MEMOIR. lit 
effects, but upon z¢seZf they cannot act. The power that drives the stone to 
the ground is “#e same whether the stone permeates water or air or vacuum, 
whether you let it fall straight, or throw it forwards, or even upwards. So, a 
certain amount of centrifugal force of variation is distributed in certain 
proportions amongst the twelve peas in the pod, and except to arrest or 
retard the progress and amount of development of the individuals or their 
organs (I incline to think), local circumstances are powerless. Give more 
nitrogen to pea No.1, and you will have more and greener leaves; but its 
seeds again will not be as green if they too are not supplied with nitrogen. 
‘‘T think my long letter will disgust you with asking any more questions, 
but I should be greatly obliged if you have time and would write me again 
on the subject. I know no one but yourself who is really thinking out 
Darwin’s views to any purpose in zoology. I am sure that with you, as with 
me, the more you think the less occasion you will see for anything but time 
and natural selection to effect change; and that this view is the simplest 
and clearest in the present state of science, is one advantage at any rate. 
Indeed, I think that it is, in the present state of the inquiry, the legitimate 
position to take up; it is time enough to bother our heads with the second 
secondary cause when there is some evidence of it, or some demand for it— 
at present I do not see one or other, and so feel inclined to renounce any 
other for the present. It is not so very long since I thought differently, and 
that variation was the first effect of circumstances on the individual. 
‘‘T hope when you next come to town you will let me know, and that we 
may have some more boxes of butterflies at the Linnean, and get the many 
curious facts you name well impressed in the languid circulation of the 
entomologists. 
‘« Ever most truly yours, 
“« Jos. D. HOOKER.” 
Hl. W. Bates to Dr. 3. D. Hooker. 
‘KING STREET, LEICESTER, March sth, 1862. 
““MY DEAR SIR, 
‘*T have not been quick to answer your last, not only because most 
of my writing time is just now taken up by my book of Travels, but 
because your letter was so full of new observations on the most difficult of all 
natural history subjects that it required long consideration. I hope you 
will attend to mine only when you have nothing else to do. 
“The view you propound of the origin of species—by the natural selection 
of varieties, which always occur as a universal condition of reproduction, in 
organic species, independent of the direct action of external conditions, is" 
simple and grand. As you say, it recommends itself by its simplicity and 
clearness, and is amply sufficient to explain the origin of species. But what 
if the real state of things is not so simple as this? Are there not some 
phenomena in species which seem to show that local conditions, and use 
and disuse, have some direct effect on individuals, the effect being propagated 
to the offspring, and so complicating the question of the origin of species ? 
Whilst I was travelling I used to attribute, like many others, the production 
of distinct local varieties, or races, to the direct action of the local conditions; 
