The following letter records a very interesting observation which is new to me, and I should be glad to hear if any similar fact has been noted before. If not, it would be very interesting if those who have the opportunity would, in the coming spring, seek for as many nests as possible of the red-backed shrike, and see if they can find any correlation between the colours of the eggs and the lining material of the nest.

Parkstone, November 1.
Alfred R. Wallace.

"Merchant Taylors' School, Crosby, Liverpool,
"October 15, 1889.

    "Dear Sir,--I wish to bring before your notice an observation of mine relative to the purpose of colour in animals.

    "The red-backed shrike (Lanius collurio). Colour of eggs--either pale blue or green, white ground with zone of spots at larger end; or, pink ground with reddish spots.

    "Observation.--The colour of the lining substance of the nest--such as roots--assimilates to the colour of the eggs, being dirty gray material when the eggs are to be pale (blue or green) white, but being of red-brown roots, &c., when the eggs are to be pink.

    "Evidence for above statement. About sixteen years ago I was a lad of fifteen, an enthusiastic birds'-nester, living at Maidstone, and found several (I forget how many) nests, and noticed this; and it so puzzled me--because I could not make out how the bird knew what coloured lining to select, because she made her nest before she laid her eggs--that I have never forgotten it. In those days I had never heard of 'The Origin of Species,' nor did I trouble myself about evolutionary theories, knowing nothing about them, so that there was no predisposing cause in me to make a wrong observation. Yet I remember it was only a school-boy's observation, and therefore it needs confirmation.

    "Assume the fact. Protective, obviously. Yet, how does the bird know? We know birds build nests from observing other nests, and not by instinct wholly.

    "(a) Have we here incipient species, in which the young, emerging from pink eggs, remember their own infancy in a reddish nest?

    "(b) Has the sight of the red lining an influence over the mother to tinge the eggs pink--i.e. would a shrike brought up in a pink cage be more likely to lay pink eggs? or a gray rabbit in a black or white hutch have a greater proportion of black or white variants in her litter?

    "(c) A mere coincidence; too few observations.

    "Will you forgive one who intends to be amongst your audience on October 29 and 30, if not prevented, thus trespassing on your time--time which, spent in research, is so valuable to the whole scientific world? Yet, I do think my boyhood's observation is worth recording, if only to direct other observers.

    "E.g. has the amount of white quartzite veins in a cliff, or chalk, any influence in the percentage of white, as against blue, eggs of the common guillemot?

"Believe me, yours faithfully,
"(Rev.) Fred. F. Grensted."