Observations on the Cuckoo. 449 
prove very decisively. Upon comparing the 
ovarium, or racemus vitellorum, of a female 
euckoo, killed just as she had begun to lay, 
with that of a pullet killed just in the same state, 
no essential difference appeared : the uterus of 
each contained an egg perfectly formed, and 
ready for exclusion; and the ovarium exhibit- 
ed a large cluster of eggs gradually advanced 
from avery diminutive size, to the greatest 
the yolk acquires before it is received into the 
oviduct.’ The appearance of one killed on the 
third of July was very different. In thisa 
great number of the membranes which had 
discharged yolks into the oviduct might be 
distinctly traced, and one of them apveared as 
ifit had parted with a yolk on the preceding 
day. ‘The ovarium still exhibited a cluster 
of enlarged eggs, but the most forward of them 
was scarcely larger than a mustard seed, 
It plainly appears, Mr. Jenner remarks, 
that birds can keep back or bring forward their 
eggs (under certain limitations) at any time 
during the season appointed for them to lay; 
but the cuckoo, not being subject to the com- 
mon interruptions, goes on laying from the time 
she begins, till the eve of her departure from 
this country; for, although old cuckoos gene- 
rally take their leave in the first week of July, 
yet instances are not wanting of eggs having 
o GL 
