266 
IW ATROLAS 
[Fan. 6, 1870 
point of the German authors®* cited by Dr. Baldamus, I will here 
adduce the following passages :— ; : 
“Quant au genre Coucou (Czcz/us) et notamment a lespéce 
type du genre, notre Coucou Chanteur (C. canorus), on_ sait 
quelle étonnante diversité offre la coloration de son ceuf, toujours 
de forme ovée, diversité telle que nous nous abstiendrons 
den aborder la description deétaillée.’—DrEs Murs, Zraité 
Général a’ Oologie Ornithclogique, &c. Paris: 1860, p. 219. 
“Ces ceufs sont trés-petits relativement a la taille de l’oiseau, et 
varient beaucoup pour la couleur. Ils sont ou cendrés, ou 
roussatres, ou verdatres, ou bleuatres avec des taches petites et 
grandes, rares ou nombreuses, d’un cendré foncé, vineuses, 
olivatres ou brunes, avec quelques points et parfois des traits déliés 
noiratres. Nous en possédons deux du blanc le plus pur, et 
un autre d’une seule teinte bleu-verdatre, pris dans un nid de 
Stapazin.”—DEGLAND et GERBE, Ornithologie Européenne, &c. 
Paris: 1867, vol. i. p. 163. 
I produce this testimony as to facts with the greater confidence, 
because the ofz7zons of the witnesses differ from my own, and not 
one of them, so far as I can gather from their works, was 
acquainted with Dr. Baldamus’s essay. 
2 and 3. “ Were these [sixteen varieties of eggs] seen to be 
deposited by the bird, or how were they identified as those of 
the cuckow?. . .. Is there not room for error here?” 
The evidence on which the eggs in question were referred to 
the Cuckow has been printed in full by Dr. Baldamus and the 
translator of his essay. To repeat it here would occupy much 
space and, I think, be unnecessary. It is of much the same kind 
as the evidence with regard to most Cuckows’ eggs. I will freely 
grant that it might be more satisfactory—if it were so my former 
paper would never have been written, since naturalists must then 
have at once accepted the theory. But, on the other hand, I have 
a right to ask this: If the eggs in question were not Cuckows’, 
what birds laid them? Surely not those in whose nests they 
were found, because it is a fact which most oologists will confirm, 
that when birds lay larger eggs than usual the colouring is 
commonly less deep, and though exceptions may occasionally be 
found, yet here we have sixteen which are at the same time larger 
than usual, and of a colour at least as deep, supposing them to 
belong to the nest-owners. Szxfee cases are too many to be 
exceptional, but this is the number only of the specimens figured 
by Dr. Baldamus; upwards of six¢y are more or less fully 
described by him. 
4. ‘* How then is this process effected ?” 
In answer to this, Mr. Sterland quotes a very brief summary of 
my own explanation, to which I have nothing now to add. 
5 to 9. The next five questions, for brevity’s sake, I will not 
repeat. They are very pertinent, but are far more easily asked 
than answered, for they open a wide field of speculation and 
investigation, since all the hitherto unexplained phenomena of 
“*Dimorphism,” ‘‘ Trimorphism,” and ‘‘ Polymorphism,” seem 
to enter here. But with respect to one of the questions (No.6), 
I submit that even if there were no other instance satisfying the 
conditions imposed by Mr, Sterland than that which I alleged, 
it is no true argument against the truth of what I advanced. 
But I think there is an indication of it in other species bearing 
very directly on the point. Take the Blackcap Warbler and the 
Tree-Pipit. The eggs of the first are well known to present at 
least two very different appearances, and those of the second are 
still more variable. Since Mr. Sterland will not allow that my 
Eagles fulfil his conditions (and of course he has a perfect right 
to do so), perhaps he will permit me to bring forward these birds. 
I have some reason for believing that the same hen Blackcap 
constantly lays eggs of similar colour. Do the birds of this 
species hatched from eggs with reddish shells lay eggs of the 
same character, or brownish ones, and zice versé? If of the 
same character, we have such an example as is required. If of 
the other colour, it becomes a case in some measure of ‘‘ Alter- 
nate Generation,” but still reducible toa law. That there should 
be no law at all seems to me at least unlikely, though I fear its 
discovery is hard. 
Certain facts of Dimorphism and Polymorphism are known, 
but I have not met with any attempted explanation of the phe- 
* They are Naumann, Thienemann, Brehm, Gloger, and Von Homeyer. 
Unfortunately, Dr. Baldamus does not refer to the passages in their writings 
wherein this opinion is expressed ; and as most of these writings are somewhat 
voluminous, I have not always been able to find what are the passages meant. 
I presume that Mr. Sterland has been more fortunate, for he would scarcely 
doubt the assertions without knowing what they were, and I should be much 
indebted to him if he will tell me where they occur—indeed, I am uncertain 
which of the Brehms and which of the Von Homeyers is intended. 
4 
nomena even in such decided and remarkable cases as those of 
the Malayan Butterflies given by Mr. Wallace (Trans. Linn. Soc. 
vol. xxv. pp. 5-11). Why the different forms of one species of 
fapilio inhabiting the same district remain distinct is perhaps 
more unaccountable than that the different forms of Cuckows’ 
eggs should be preserved, for it does not seem to me unlikely 
that the colour of the egg and the maternal instincts should depend 
upon the 4ez bird; in which case, granting the hereditariness (if 
I may make such a word) of the qualities already specified, I 
think there would be no difficulty. 
10. A full reply to Mr. Sterland’s last question would lead me 
to anticipate much that I intend to say when you again permit 
me to trespass on your readers’ forbearance. Consequently, I 
must defer it until I come to the consideration of ‘* Cuckows’ 
Dupes.” ALFRED NEWTON 
Cambridge, Dec. 11, 1869 
By way of postscript of my letter of the 11th of December (for 
the delay in publication of which I am in no way accountable*), 
permit me to offer a few remarks on the communications of 
Mr. Dresser and Mr, Cecil Smith which have since appeared. 
Mr. Dresser says (p. 218) that he ‘‘cannot quite agree with 
Professor Newton that Cuckows’ eggs as a rude are subject to 
great variety.” I am not aware that I had made such an 
assertion. The nearest approach to it that I can find is my 
statement (p. 74), that ‘‘it has long been notorious to oologists 
that eggs of the Cuckow (7.e. of the Common Cuckow of Europe 
—the only species I had mentioned) are subject to very great 
variety,” and in proof thereof I have since furnished some other 
(and, I think, satisfactory) evidence. Mr. Dresser himself has 
also brought two or three additional examples which confirm my 
statement. For the knowledge of these I am much obliged to 
him, as well as for stating the result of his own experience in 
support of my supposition that the eggs of the same hen Cuckow 
resemble each other. 
Mr. Cecil Smith (p. 242) seems to me to be as unfortunate in 
his interpretation of my remarks as he was in that of Dr. 
Baldamus’s (p. 75, note). I feel sure that I have not “ pruned 
and paved” down the doctor's theory so “ that there is but little 
of the original left.” To the facts alleged by that naturalist I 
have taken no exception—on the contrary, I have borne witness 
(pp. 74, 75) to their general truth ; and in the attempt to offer a 
reasonable explanation of them, I am certain that my “‘manipula- 
tion” is not open to any such charge as that made by Mr. 
Smith. My ‘‘cautious and limited statement” is not different 
from that of the doctor, nor does “it entirely sweep away” a 
single assertion of his as to matters of fact. Mr. Smith, appa- 
rently, thinks because I have referred to the number of 
Cuckows’ eggs yearly found in nests of the Hedge-Sparrow in 
this country, without ever bearing any resemblance to the eggs 
of that bird—a fact, of course, fully admitted by him—that I must 
thereby deny the single exceptional case adduced from Germany 
by Dr. Baldamus ; but I have never maintained, because no 
likeness is to be traced in a great many instances, that none was 
ever perceptible, and accordingly there is no ‘issue of fact” 
between the doctor and myself. I must take the liberty of add- 
ing, that Mr. Smith, having, as I before showed, misunderstood 
Dr. Baldamus, has now misunderstood me ; and this being the 
case, it is perhaps needless for me to take up more of your 
space. ALFRED NEWTON 
January 3, 1870 
The Veined Structure of Glaciers 
I THINK there is no one point in connection with glaciers 
more interesting than their veined structure, or one upon 
which so much has been written that remains equally unsettled. 
The difference of opinion about it between the authors who have 
published most upon the subject are not less remarkable than 
the phenomenon itself : no two are agreed, except in considering 
it as a constitutional feature. 
Professor Agassiz maintains (AM/antic Monthly, Dec. 1863) 
that the horizontal layers of pure ice which are formed between 
the beds of snow from which a glacier is born, constitute many 
of the identical veins or plates of pure ice which pervade the 
glacier when it is in full life and activity; and attributes the 
inclination which they make, in the latter case, to their former 
horizontal position, to the contortion, bending, or folding, to 
* [The delay in the publication of Prof. Newton's letter is owing to an 
oversight. It was received prior to the communications of Mr. Dresser and 
Mr, Cecil Smith, printed in our eighth and ninth numbers,—Eb. ] 
