||P.199 right column top paragraph: "If the mutation rate is known, either from a direct experimental estimate or from data on DNA sequence divergence between species with known dates of separation, Ne can be estimated as π/(4u), where π is nucleotide site diversity. Some examples are shown in Table 1. Second, for very small populations, such as those used in animal and plant breeding or in the captive breeding of endangered species, Ne can be estimated from observed changes between generations in the frequencies of putatively neutral variants (refs 9, 58, 59, 60)." P.200 right column 3rd paragraph: "A reduction in Ne below N reduces the efficacy of selection compared with a Wright–Fisher population of size N. This result applies to a wide variety of causes of reduced Ne, as [investigators] shall see in the next section. Given the large values of long-term Ne in Table 1, weak selection can therefore be very effective in evolution, as was strongly emphasized by Fisher (ref 68)."