152 THE BIRDS OF SHERWOOD FOREST. 
that in the alleged instances the young of the goatsucker 
has been mistaken for that of the cuckoo—a mistake 
which might easily be made, from the similarity of the 
plumage of the young of both species. 
The mode in which the cuckoo introduces her egg 
into the nest of another bird has been made a greater 
difficulty of than necessary, from the fact that usually it 
would be a physical impossibility for the cuckoo to enter 
the nest and lay her egg in the ordinary manner. I 
have often found the egg, but never, (except in one 
instance, where the shallow nest of the pied wagtail was 
chosen), was the nest in such a position as to be reached 
by the cuckoo otherwise than with her bill. The latter 
is doubtless the instrument by which the egg is deposited 
in its chosen place. 
But of all the extraordinary theories which have been 
brought forward respecting the cuckoo, that advanced 
by Dr. Baldamus of Stuttgart is the most amazing. It 
was first published by him in 1853 in the Vawmanmia, 
the leading ornithological periodical of Germany, but 
had remained unknown to English naturalists until the 
Rey. A. C. Smith called attention to it in the Zoologist 
for March, 1868, and gave a translation of Dr. Baldamus's 
paper in that periodical for the following month. 1[ 
would advise all my readers who are interested in the 
subject to peruse that article for themselves, but for 
those who have no opportunity of doing so I will give a 
brief outline of the theory. Dr. Baldamus begins by 
asserting that the eggs of the cuckoo are subject to great 
variation, both in colour and markings, and that he had 
found thirty-seven varieties! He then set himself to 
discover the cause of this singular variability, and after 
some time spent in diligent research and examination, 
