Now neither fishes nor any animals devoid of feet are
furnished with testicles, but male serpents and male fishes have a
pair of ducts which fill with milt or sperm at the rutting season, and
discharge, in all cases, a milk-like juice. These ducts unite, as in
birds; for birds, by the way, have their testicles in their
interior, and so have all ovipara that are furnished with feet. And
this union of the ducts is so far continued and of such extension as
to enter the receptive organ in the female.