VII 
ON THE INFERTILITY OF CROSSES 
163 
163) was the first to mention, I believe, that in different parts 
of South America the ram is more usually crossed with the 
she-goat than the sheep with the he-goat. The well-known 
‘ pellones ’ of Chile are produced by the second and third 
generation of such hybrids (Gay, ‘ Hist, de Chile/vol. i. p. 466, 
Agriculture , 1862). Hybrids bred from goat and sheep are 
called ‘ ehabin ’ in French, and ‘ cabruno ’ in Spanish. In 
Chile such hybrids are called ‘carneros lanudos their breed¬ 
ing inter se appears to be not always successful, and often the 
original cross has to be recommenced to obtain the proportion of 
three-eighths of he-goat and five-eighths of sheep, or of three- 
eighths of ram and five-eighths of she-goat; such being the 
reputed best hybrids.” 
With these numerous facts recorded by competent observers 
we can hardly doubt that races of hybrids between these very 
distinct species have been produced, and that such hybrids are 
fairly fertile inter se; and the analogous facts already given lead 
us to believe that whatever amount of infertility may at first 
exist could be eliminated by careful selection, if the crossed 
races were bred in large numbers and over a considerable area 
of country. This case is especially valuable, as showing how 
careful we should be in assuming the infertility of hybrids 
when experiments have been made with the progeny of a single 
pair, and have been continued only for one or two generations. 
Among insects one case only appears to have been recorded. 
The hybrids of two moths (Bombyx cynthia and B. arrindia) 
were proved in Paris, according to M. Quatrefages, to be fertile 
inter se for eight generations. 
Fertility of Hybrids among Plants. 
Among plants the cases of fertile hybrids are more numerous, 
owing, in part, to the large scale on which they are grown by 
gardeners and nurserymen, and to the greater facility with 
which experiments can be made. Darwin tells us that Kolreuter 
found ten cases in which two plants considered by botanists 
to be distinct species were quite fertile together, and he there¬ 
fore ranked them all as varieties of each other. In some 
cases these were grown for six to ten successive generations, but 
after a time the fertility decreased, as we saw to be the case in 
