It is well known that castration, when performed in early life and before sexual maturity has been reached, has a marked effect not only in inhibiting the development of the accessory male organs, but in changing the general conformation of the body. Thus in castrated guinea-pigs, oxen, and capons, as well as in eunuchs, the bones of the limbs tend to be abnormally long, this result depending upon an arrest in the ossification of epiphyses. The secondary male characters are also in many cases suppressed, so that there is an apparent approximation to the female type. Thus in red deer if the testes are removed in quite immature animals the antlers fail to make their appearance, and in fallow deer castration at birth limits the horn formation to the development of single dugs. Secondary sexual characters, however, are not always correlated with the presence of the essential reproductive organs, even in mammals. Thus the withers in the gelding resemble those of the horse rather than those of the mare, in which the witheres are lower. Moreover, in certain varieties of cattle in Italy, the horns in the ox, if castraction has been carried out young, are far longer than those of either the bull or the cow. Ovariotomy in the female is often said to lead to the assumption of male characters, but there is little experimental evidence that this is actually the case. In the human female complete removal of the ovaries, if carried out in early life, besides preventing the onset of puberty and the occurrence of menstruation, produces effects on the general form and appearance, individuals so operated upon being said, in some cases, to show resemblances to men. Abnormalities in the ovaries have been described as producing similar results. Thus, Rörig records three cases in which female deer possessed horns, and were shown on dissection to have had abnormal ovaries. Darwin states that female deer in old age have been known to acquire horns. It Wallace says that in old mares the neck tends to acquire an arch as in the stallion. The occasional growth of hair on the face in old women is a phenomenon of the same kind. Similar observations have been made upon birds, especially ducks, poultry, and game birds. Darwin mentions the case of a duck which, when 10 years old, acquired the plumage of the drake. Other cases are those of hens which in old age assumed secondary male characters and started to crow. Hunter mentions a hen pheasant which had male plumage associated with an abnormal ovary. Numerous other instances have been described, but it is not apparent that such an acquirement of male characters by female individuals is always correlated with an abnormality in the reproductive organs. According to Gurney the assumption of male plumage is generally associated with sterility in female gallinaceous birds, but not, as a rule, in female passerine birds. Thus Gurney describes a hen chaffinch with male plumage and a number of developing eggs.
Structural comparison of the rostra of two species of weevils coexisting on Ailanthus altissima: the response to ecological demands of egg deposition
