DOES THE CUCKOO INCUBATE ? 223 
discussing the extraordinary observations of Herr Miller, I will 
very briefly mention two more instances of the remarkable 
strength of the Cuckoo’s eggs which I think will be of interest. 
(Two such instances are then given, and Herr Walter con- 
tinues:—] I think that I have now sufliciently demonstrated 
the strength of Cuckoos’ eggs, but I can prove just as conclusively 
that one and the same Cuckoo always lays similar eggs, and 
consequently that the nest found by Herr Muller could not have 
contained the entire clutch of one Cuckoo. In proving this 
I am able to controvert one of the three arguments which Herr 
Miiller uses to support his assertions. 
The conclusions which he draws from his owr observations 
are two in number. [These have been already quoted, p. 218.] 
My observation, however, goes further, namely (3), that the 
young Cuckoo—contrary to my experience of the young of this 
species reared by the common small birds—becomes full-fledged 
in about twenty-one days, whilst young Cuckoos bred in the 
nests of song-birds, as I have observed, take six weeks to become 
capable of flight. Doubtless the reason for this rapid maturing 
of the Cuckoo in the first case is the much abundant supply of food 
brought by the parent bird. [The meaning here is very obscure.] 
The first conclusion of Herr Miiller cannot be positively 
disproved, for the matter stands thus :—TIf he asserts that he has 
positively seen the Cuckoo incubating for an hour and a half on 
the nest, and that he afterwards saw the old Cuckoo feeding the 
young ones with caterpillars, a denial would be tantamount to 
accusing him of falsehood. We can only draw our own con- 
clusions from what has been already stated. But as regards 
points 2 and 3 it can be positively shown that Herr Miiller has 
made a mistake. 
For more than ten years I have made repeated observations, 
and at the annual meeting of the “ Allgemein Deutsche Ornitholo- 
gische Gesellschaft’’ of Berlin, have proved by exhibition of eggs 
that the same female Cuckoo always lays similar eggs, so that it is 
almost superfluous to adduce fresh proofs, or to repeat old ones. 
I will therefore only refer to my own observations and those of an 
enthusiastic naturalist, Herr K. Ochs, of Cassel, and allow him 
to speak for himself. 
Herr K. Ochs has made some interesting observations on 
Cuckoos’ eggs, and knows the. Cuckoos of the Habichtwald (the 
