314 
‘“¢rmos, vi., in Compos.; it expressed anything /arge or coarse, 
as in our horse-chestnut, horse-laugh ; v. tid-xpnuvos,-uapabpoy, 
-céAwwoy, -Tupia, -opvos ; cf. Bou-.” 
Long Ditton, Kingston, Aug. 5 
The Rotundity of the Earth 
WE have seen the statement signed ‘* Parallax,” at page 236 
of No. 38 of NATuRE, and shall be obliged if you will afford 
tls an opportunity of briefly saying in reply, that when we tried 
the ‘‘ flag experiment,” the person calling himself ‘‘ Parallax” 
was not present. 
The experiment was conducted in his absence, as he did not 
come at the time appointed. He did not come at all that we 
know of ; we did not see him. J. NEWBEGIN 
Norwich, August 10 C. W. MILLARD 
W. H. Dakin 
M. W. MoGGrIDGE 
Cuckow’s Eggs 
A sHortT timeago I addressed you on the subject of Cuckow’s 
eggs, giving you some experiences of my own. I now have 
much pleasure in forwarding to you a portion of a letter on the 
same subject from an esteemed and obseryant correspondent, 
Mrs. Barber, of Highlands, near Graham’s Town, to whom I 
communicated the substance of my letter to you. Mrs. Barber's 
name is well known in the botanical world as a most accurate 
scientific observer ; of her ornithological acuteness my work on 
the Birds of South Africa amply testifies, and you may place 
full confidence in the statements she has made in this communi- 
‘cation, 
Cape Town, June 1870 Ep. LAYARD 
“ Your remarks on the eggs of the cuckow tribe are very in- 
teresting. I confess that Iam a believer in natural selection, 
and Darwinian in my opinions, but nevertheless in this matter I 
do not see the necessity for the intervention of natural selection ; 
however, I hope you will bear in mind that I am speaking only 
with regard to the cuckows of my own country (South Africa), 
and as far as my vbservation extends, the eggs of these birds 
bear no resemblance to those of the birds upon which they are 
parasitic. 
“Many of the different species of the cuckows of this country 
lay white eggs ; the whole of those included in the genus Cha/- 
cites produce white eggs, the birds upon which they are parasitic 
are the various species of Arizgi//ide, they do not, however, 
confine themselves entirely to this tribe. 
“‘T have frequently seen the eggs of the ‘Dedric’ (Chalcites 
auralus) and the ‘ Metje’ (C. 4/aasii) in the nest of the Cape 
canary (Avingilla canicollis) and the ‘ Streep Koppie’ (Aringil/ar ia 
vitiata), where they were conspicuous not only for their pure 
white unspotted appearance, but for their size also, which is 
nearly twice that of the Cape canary, and considerably larger 
than the eggs of the ‘Streep Koppie.’ 
“‘T have also found the egg of the ‘ Dedric’ in the nest of 
the green Sun-bird (Vecfarinia famosa), where it was also much 
larger than the grey speckled eggs of the sun-bird, and likewise 
dissimilar from its pure white colour. 
“The egg of Cucudus solitarius is of a dark mahogany brown, 
and this egg I have seen in the nest of the wood robin (Zesso- 
norius phenicurus), when its difference was obvious both in 
size and colour, my son (F. H. Barber) found one of these dark 
brown eggs in the nest of the Cape canary ! and despite its 
great dissimilarity compared to the small white speckled eggs of 
that bird, the work of incubation was quietly going on. 
‘©The birds upon which the ‘ Honey Guides’ are parasitic are 
Laimodon leucomelas (vel L. unidentatus). 1 have frequently seen 
them at the nests of these birds, where great conflicts vecasionally 
take place between the /ndicators and Laimodons, the latter being 
fully aware that the ‘ Honey Guide’ is an intruder, the egg of 
the Zaimodon is speckled, that of the Zdicator white. 
“The ‘October bird’ (Oxy/ophus edolius) deposits her white 
eggs in the nest of the large woodpecker ; my brother (Bertram 
Bowker) once met with ¢/7vee of the young of this cuckow in the 
nest of that bird ; it is not a common occurrence, I believe, that 
so many eggs should have been deposited in a single nest ; the 
large woodpecker is, however, eyual in size to the ‘October 
bird ;’ when the birds upon which they are parasitic are smaller, 
the cuckow deposits but one egg, as the food and space required 
will in that case be only sufficient for a single individual. 
“In the nest of the green sun-bird (Mectarinia famosa) I once 
observed a young ‘Dedric,’ which nearly filled the nest, It 
NATURE 
[Aug. 18, 1870 
was not quite full fledged, and its frequent calls for food induced 
the sun-birds (both male and female) to exert themselves to 
the utmost, and in fact they had to work hard to satisfy the cray- 
ings of this greedy intruder ; however they did it witha good will, 
and apparently without any suspicion that they were being im- 
posed upon. Birds in general have no suspicion on this score, 
they suspect no trickery, and are therefore willing to incubate 
any kind of egg, provided it is not too large to fill up the nest. 
I think I told you how I had occasionally changed the eggs of 
yarious species of birds from one nest to another, making fearful 
confusion in consequence, yet the owners of the nests never 
suspected that anything was wrong, but proceeded quietly with 
their work. With regard to eggs, the discriminating power of 
birds is very obtuse, in fact they have none at all, and therefore 
in this case the agency of natural selection would not come into 
play ; it would not be required. In nature there is no waste, no 
failure, no useless expenditure of time and ingenuity, every 
arrangement is sufficiently perfect to work out its own end with- 
out being overstrained or overwrought,—M. E. BARBER,” 
Special Modification of Colour in the Cushat 
IN reading the chapter on ‘‘ Mimicry,” in Mr. Wallace’s yalu- 
able collection of essays lately published, I was struck by a 
remark there made in regard to the special modification of the 
colour of the wood-pigeon. It is stated (p. 53), on the authority 
of Mr. Lester, that ‘the wood-dove, when perched amongst the 
branches of its favourite fir, is scarcely discernible, whereas, were 
itamong some lighter foliage, the blue and purple tints in its 
plumage would far sooner betray it.” ‘This description may be 
accurate enough in regard to Co/umba enas, but our experience 
is against its application to Columba palumbus. It was acommon 
pastime of our boyhood to stalk the cushats in a mixed wood of 
the usual Scotch trees, and while familiar enough with their 
habit of making their nests in the spruce, unquestionably their 
favourite perches were on beeches and other hard-wood trees, 
Even after surmounting the somewhat delicate task of approach- 
ing the roosting-place of a cushat, it was no easy matter to detect 
the bird, except by its note, so closely did its general colours 
blend with the smooth, lichen-coyered boughs of the beech, 
even where no leaves intercepted the view. The bird appears 
to build its nest especially in the spruce, not because its general 
colour agrees therewith (which it does not), but because the 
thick nature of the foliage and branches gives it, the eggs and 
young, sufficient privacy. Underall other circumstances it prefers 
to perch on the beech and other hard-wood trees, where its 
colours so adapt it for concealment. Of course the casual 
alighting on the pinnacles of the spruce during the breeding 
season is of little moment in the present question. 
W. C. McInrosit 
Colcur Blindness 
ALTHOUGH I have no intention of discussing the theory of 
colour-blindness propounded by Mr. Monck in Nature of 
July 28, it may not be inopportune, while the subject is under 
the notice of your readers, to call their attention to a peculiarity 
with respect to the percepticn of colour, of which I have been 
able to discover no instance. 
Some years ago I wassitting in a charel opposite to a stained 
glass window, a portion of which (towards my left) was hidden 
from me by a pillar, and I observed that, as I moved my head 
to the right, the window flashed out into brillianey where it had 
appeared dull before, while the contrary effect was produced as 
I moved my head to the left. On examining the conditions of 
the phenomenon carefully I found that it was due to the fact 
(which I had not the least suspected before) that my right eye 
is distinctly less sensitive to colour than my left. This I have 
since verified in various ways, though the difference is not very 
easily perceived unless the colours are brilliant, as in stained glass, 
bright coloured flowers, many of Turner’s pictures, &e. The 
difference consists in this, that all colours appear less bright, or, 
as I should say, gvever, when seen with the right eye, and the 
more delicate gradations of colour cease to be perceived, while 
in many cases of even strongly contrasted colours, I should find 
it difficult to distinguish them with certainty with the right eye, 
especially if [had not previously seen them with the other eye. 
I have found too that the central part of the retina of my right, 
eye is more defective as to the perception of colour than the 
lateral portions, since in looking at an extended surface of a 
