ABSTRACT
THERE are men in northern countries who keep fish-ponds, which they have constructed because of the remarkable profit that can be gained from certain fish. 1 From time to time they let out the water and drain the ponds so that they may clear them of fish. When not a single one remains they leave the pools empty, ready for another variety to be introduced. Later, after they have been filled with water and new specimens put in, the spawn of the former fishes, which lies hidden in the slime, gives rise to some of the old species, and these are observed to increase in number more than those that have just been inserted. 2 This is not unlike those fish in the Egyptian Nile which, after a year has elapsed and the waters have flowed back, grow into life again, in what seem countless numbers, from the spawn that has been scattered and lain in the mud once the river has receded.
