100 ZYGODACTYLI. CUCULUS, Cuckoe. 
would be difficult to account for some phenomena connected 
with its history. 
The continuation of the species appears to require such a 
provision to have been granted, for, as he observes, if the 
cuckoo was obliged, like other birds, to lay its eggs, five or 
six in number, successively day after day, it is hardly pro- 
bable it should find (within that time) sufficient nests in the 
exact state to receive them; much less, if it laid a greater 
number of eggs, as has been suggested. The rare occur- 
rence of the cuckoo’s egg being found, gives additional 
strength to this supposition, for although the old birds may 
be seen in abundance, such a discovery has seldom been 
made. 
Naturalists have been puzzled to account for this bird not 
performing the office of mcubation, but as their researches 
have principally been directed to the anatomical structure, 
in which point it does not essentially differ from many others 
that perform this office, we arrive by these means at nothing 
satisfactory. The above peculiarity of this remarkable genus 
must not probably be looked for in any principle of confor- 
mation, but must be explained from their habits and eco- — 
nomy. 
. Let it be remembered these birds are migratory, and that 
the period during which the adults remain with us, is very 
short ; but the propagation of the species must be effected 
during that period. Now, as their arrival does not take place 
before the month of April, and the egg is seldom ready for 
incubation before the middle of May, there would not be a 
sufficient length of time for the young to be hatched, or 
(making every allowance,) sufficiently fledged to accompany 
the old birds at the period of their departure, which seldom 
or never extends beyond the first week in July. 
The egg requires a fortnight’s meubation, and the young 
are not able to fly in less than five or six weeks, which facts 
have been ascertained from repeated observation. 
