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 78 -THE CON:DOR Vol. XXI young capon in whose body the ovaries of a hen are grafted, will develop the featbering characteristic of the hen. The capon without the engrafted ovaries, will develop almost as the normal male. A normal female rabbit, treated by hypodermic injection with the extract of foetus in normal salt solution, will pluck the fur from her breast and build a nest as though expecting a litter of her own young, though none are developing. In these two cases a .structural and a psychologic character, respectively, are influenced by a physiologic agent --a particular chemical substance. This substance is secreted and thrown into the blood stream by the germ cell or by the developing ovum, and constitutes one of those products,' so important to the highly organized animal, which we term internal secretions. The germ cells in birds, like those in most other wild animals, are season- ally active. As a result the reproductive gland may increase or di- minish in size from ten to one hundred fold in regular cycles, which cycles are generally conformable to season. With the fluctuation in mass there will be a change in the amount and possibly in the nature of the internal secretion, hence the whole physiologic balance of the body will be seaso. nally affected. It is doubtless because of this ebb and flood o the physiologic tide that certain in- .stincts, particularly those connected with the reproductive process, appear and disappear in orderly sequence each year. It is maintained that the choosing of a mate is a purely instinctive act' on the part of the wild bird. (It might often be discovered to be so among our august selves !) The choice is part of a great chain of events connected with the reproductive process as a whole l it is physiologic in its immediate origin, and therefore is of seasonal recurrence. During the dormant period of its re- productive cells, the bird is practically an asexual creature. Malehess and fe- malehess have disappeared entirely so far as interests, many activities, and often external appearance, are concerned. On the other hand,' resuinptiol o the germ cell activity initiates a new mating activity. The bird chooses a new mate. So much for the theorist. What have.we from the field observer? Among the forces that hold individuals together in the bird worldi we may recognize at least three bonds, the parental tie, the marital tie, and the social tie. Of these three, which is of most importance as a bond of some duration? I con- tend that the parental tie is of greatest surviva] value to the race. We find it lacking in but few species, notably in cowbirds, in Old-World cuckoos, and in megapodes. But in these species the marital tie is also lacking as a persistent bond. The flocking tie alone, persisting in the cowbirds, results in a reprehensi- ble Bohemian freedom and a Gypsy-like vagrancy of most unavian character. Upon the duration of the parental tie, the whole care of the young and hence the safety o the race is hinged. It must out]ast the period of the young.'s dependency, while the marital tie is not absolutely necessary beyond the mo- mentary contact required for impregnation. W.e actually see the parental tie ruptured. The parent weans her young because of waning instinet, and fur- ther support is denied it. The parent and her offspring then become rivals, peaceful or otherwise. If such a fundamental tie be ruptured, why not also the less necessary marira] bond ? We find at least circumstantial evidence bear- ing upon the question. At the close of the breeding season a thousand Linnets assemble in a weed patch, there to feed from time to time during the fall and winter. The flock