42 
MANUAL OF TAXIDERMY. 
testicles will be nearly or quite a half inch in dia- 
meter, whereas in autumn they will not exceed a 
number eight shot in size ; and in nestlings of the 
same species they are not larger than a small pellet 
of dust-shot. At this early age, the sex of birds 
which have become somewhat soft is quite difficult 
to determine, and the same is true at any season 
if the specimens be badly shot up. There are 
other organs, however, in the male. For example, 
the sperm ducts are always present, appearing like 
two white lines ; and in the breeding season the 
plexus of nerves and arteries about the vent be- 
comes swollen, forming two prominent tubercles 
on either side (Fig. 6, 3, 3). 
In the female the ovaries lie on the right side 
(Fig. 7, 2) in about the same position as is occupied 
