NOTE ON THE ORIGIN OF SEXUAL DIMORPHISM,
AND OF NUPTIAL WEAPONS AND ORNAMENT-
ATION.
Not long ago[1] I suggested, from a consideration of the spawning habits of the various species of Oncorhynchus, that secondary sexual characters, as well as the seasonal assumption of nuptial ornaments and weapons, might have had their origin in pathological conditions: that the whole metabolism of the animal is upset in the effort to produce the sexual products, with a result that pigment and matter are set loose in the body, and find their way to new regions, often with a fatal—always with a serious—influence on the animal, but resulting in the production of nuptial adornments and weapons. Mr. Cunningham, in parts of his argument,[2] comes very near this hypothesis—for instance, when he lays great stress on the influence of the veins as a controlling factor in the evolution of sexual characters. Nevertheless, he is most unfortunate to have missed the Reports of Investigations on the Life-History of Salmon, published by the Fishery Board of Scotland. In these papers both his and my views are supported, and it is clearly shown that in the breeding Salmon, whether male or female, such transference of pigment and matter, both of fats, proteids, phosphorus compounds, and iron, actually does take place.
There remains yet another point upon which I wish to touch. Many naturalists base their arguments on the absence of proof that acquired characters are or can be inherited. Here they have a strong position; but, considering the matter closely, do we find that secondary sexual characters are in all cases inherited? The form and detail of an animal's body exist as the expression of, or owe their structure to, two forces, the one purely vegetative, or due to purely nutritive causes, the other sexual.
