Nov. 18, 1869] 
NAT ORE 
75 
that his published figures represent the specimens (sixteen 
in number) from which they are drawn, as faithfully as 
figures of eggs usually do, and that an inspection of the 
series convinced me that the belief he entertained was not 
groundless. All the eggs in question, some departing very 
widely from what I had been used to regard as the normal 
colouring, bore an unmistakable resemblance to those of 
the birds in the nests of which they were asserted (in 
most cases, I was assured, on very good authority) to have 
been found ; while in some cases there was just enough 
difference between them and those they “mimicked,” to 
show that it was far more unlikely that they should have 
been extraordinary varieties of the eggs of the species in 
question, than eggs of the Cuckow. 
Dr. Baldamus’s allegation therefore seemed to me to be 
in part proved. If the history of the eggs before me 
could be trusted—and I had no reason to doubt it, the fact 
of the likeness was in many respects self-evident, in others 
certainly not so striking, and in some perhaps question- 
able. In further corroboration of the theory also, there 
were the similar instances cited with much assiduity from 
foreign sources by Dr. Baldamus in his essay,* and one, 
apparently not known to him, but given by Mr. Blyth in Sir 
William Jardine’s “Contributions to Ornithology” for 1850 
(p. 69 ézs, pl. 52). Another and very remarkable case had 
also come to my own knowledge. In the autumn of 1857 
I had received from Mr. Tristram all the eggs collected 
by him in Algeria during the preceding season. When 
they were unpacked, it appeared that there were two more 
specimens of the egg of a large North-African Cuckow 
(Oxylophus glandartus) than I had been led by him to 
expect. On examination, I found that the first two eggs 
of this species which had been obtained by him so much 
resembled eggs of the Magpie of the country (Pica meaure- 
tanica), in the nests of which they had been found, that, 
skilful oologist as he was, they had passed, even to his 
practised though unsuspecting eye, as those of the latter 
bird. Had I known then of Salerne’s words, I should 
have exclaimed with him, “c’est une chose incompréhen- 
sible!” 
Having said thus much, and believing as I do the 
Doctor to be partty justified in the carefully-worded 
enunciation of what he calls a “ Law of Nature,” I must 
now declare that it is only “approximately” and by no 
means wziversally true that the Cuckow’s egg is coloured 
like those of the victims of her imposition. Increase as 
we may, by renewed observations, the number of cases 
which bear in favour of his theory, yet, as almost every 
bird’s-nesting boy knows, the instances in which we can- 
not, even by dint of straining our fancy, see resemblances 
where none exist, are still so numerous as to preclude me 
from believing in the generality of the practice imputed to 
the Cuckow. In proof of this I have only to mention the 
many eggs of that bird which are yearly found in nests of 
the Hedge-Sparrow in this country, without ever bearing 
the faintest similarity to its well-known green-blue eggs 
One may grant that an ordinary English Cuckow’s egg 
will pass well enough, in the eyes of the dupe, for that of 
a Titlark, a Pied Wagtail, or a Reed-Wren, which, accord- 
ing to my experience, are the most common foster-parents 
* I do not here enumerate them; they will be found in Nawmannia for 
1853, p- 317, note. The plate which illustrates the paper is in the volume of 
the same magazine for the following year. 
of the Cuckow in this country ; and indeed one may say, 
perhaps, that such an egg is a compromise between the 
three, or a resultant, perhaps, of three opposing forces ; 
but any likeness between the Hedge-Sparrow’s egg and 
the Cuckow’s, so often found along side of it, or in its place, 
is not to be traced by the most fertile imagination. We 
must keep therefore strictly to the letter of the law laid 
down by Dr. Baldamus, and the practice imputed to the 
Cuckow is not universally but only “approximately ” 
followed. 
Now, is it possible to give a satisfactory explanation of 
the process by which the facts alleged are produced? Dr. 
Baldamus assigns none. He lays down a number of 
aphorisms, most of which are very interesting, and, I 
believe, true ; but they do not touch the question. A good 
many people who have only read hastily, and still more those 
who have to all appearance only read at second or third- 
hand what has been written on the subject, seem to imagine 
that the Doctor has wished to assert that the Cuckow can 
voluntarily influence the colour of her egg, so as to assimi- 
late it to those already in the nest in which she is about to 
deposit it.* Dr. Baldamus, indeed, mentions such a sup- 
position, but expressly says that he rejects it, and herein I 
think that nearly every physiologist will agree with him. 
It will be admitted, I think, that Dr. Baldamus’s in- 
ference as to the object of the practice being that the 
Cuckow’s egg should be “less easily recognised by the 
foster-parents as a substituted one,” is likely to be true. 
This being the case, only one explanation of the process 
can to my mind be offered. Every person who has studied 
the habits of animals with sufficient attention will be con- 
versant with the tendency which certain of those habits 
have to become hereditary. It is, I am sure, no violent 
hypothesis to suppose that there is a very reasonable 
probability of each Cuckow most commonly placing her 
eggs in the nests of the same species of bird, and of this 
habit being transmitted to her posterity. Without attri- 
buting any wonderful sagacity to the Cuckow, it does seem 
likely that the bird which once successfully deposited her 
eggs in a Reed-Wren’s or a Titlark’s nest should again seek 
for another Reed-Wren’s or another Titlark’s nest (as the 
case may be), whenshe had an egg to dispose of, and that she 
should continue her practice from one season to another, 
We know that year after year the same migratory bird 
will return to the same locality, and build its nest in almost 
the same spot. Though the Cuckow be somewhat of a 
vagrant, there is no improbability of her being subject to 
thus much regularity of habit, and, indeed, such has been 
asserted as an observed fact. If then this be so, there is 
every probability of her offspring inheriting the same habit, 
and the daughter of a Cuckow which always placed her egg 
in a Reed-Wren’s or a Titlark’s nest doing the like. 
Further, I am in a position to maintain positively that 
there is a family likeness between the eggs laid by the 
same bird, even at an interval of many years. I know of 
more than one case in which a particular Golden Eagle 
has gone on season after season laying eggs that could be 
at once distinguished by a practised eye from the eggs of 
almost any other Golden Eagle; and I know of one case 
* Thus Mr. Cecil Smith (not to be confounded with Mr. A. C. Smith, 
before mentioned) in a work published within the last few weeks, falls into 
this mistake (“ Birds of Somersetshire,” p- 265), after having stigmatised the 
Doctor's theory as “ wild,” which he ell might if it had been as it is repre~ 
sented, 
