THE COLORATION PROBLEMS. 245 
tinctly hostile one, since it showed a greater alacrity, I thought, to help 
the opponents than the supporters. One of his notes in particular, 
viz., that in the Hntomologist [1918], p. 292, confirmed my view. 
I should certainly not condemn an attitude of real neutrality, but 
Col. Manders (Ft. Record, vol. xxv., l.c.) classes the Batesian and 
Miillerian theories as working hypotheses, a distinctly less reputable 
class than the class amongst which theories are wont to congre- 
gate. Nor do I consider that my claim for universality of a theory 
would necessitate the belief that the Rev. Geo. Wheeler was a religious 
sceptic. Before leaving that part of my paper, may I remind Mr. 
Wheeler that his hopes have not yet materialized into the as yet 
adumbrated comments on experiments with birds in confinement, and 
I feel sure his comments would be of the greatest interest. 
Now as to Mr. Colthrup, who really seems irrepressible. I shall 
first place on record all the information I have been able to find time 
to record since my last paper, and I will then discuss the evidence and 
deal with Mr. Colthrup’s arguments. Whatever may be the value of 
our respective arguments and opinions, I believe that our respective 
observations must have a value, and both of us, I have recently dis- 
covered, have been calling the camera to our aid as a means of record- 
ing facts, and Mr. Colthrup is no mean performer with his apparatus, 
and shows a very full appreciation of what exceedingly dissimilar 
visual results can be obtained from the same subject by different modes 
of treatment. I shall discuss this more fully later on in the light of 
recent knowledge as to screens, plate and developers. 
The last observation I appear to have recorded was under date 
April 5th, 1918. After that date both my brother and I cast around 
in our minds for some consistent practice in observation which would 
enable us to watch birds more closely, and more continuously, and as 
my brother is primarily a “ birdman ” we decided that the photography 
of birds feeding young at the nest offered great attractions. 
It promised the opportunity of close and continuous study at a time 
when insect life was abundant. This promise was fulfilled ; in other 
respects, however, we found that the scheme was not so good as it 
promised to be. All our birds do quite a great deal of their feeding of 
young, even up to within a few hours of the time that the young quit 
the nest, by regurgitation. As might be expected this rendered it 
almost impossible to be certain what the bird had swallowed, and it 
was only on the’ rarest occasions that we could conjecture what the 
pabulum had been. 
It was a source of genuine vexation to both of us that what we 
regarded as our two most hopeful birds, viz., Dryobates major sub-sp. 
anglicus, the Great Spotted Woodpecker, and Picus viridis sub-sp. 
fluvius, the Green Woodpecker, fed by regurgitation so habitually. 
Another bird, Caprimulgus europaeus, the Nightjar, fed solely at a 
time when we were unable to see. Had we been living in times of 
profound peace we should have turned a search-light on to see what we 
could, but we are in a prohibited area (a military area, a munitions 
area, and a naval base), so we should merely have been a nuisance and 
got into trouble. 
Another cause of disappointment was that the quickness of the 
birds, coupled with the smallness of our peepholes (which must be 
kept small), rendered it very difficult often to get a good enough look 
