The lower we descend in the scale of animal life in our survey of behaviour during the reproductive period, the more the evidence seems to grow in favour of the interpretation of the Sexual selection theory adopted in these pages—the view that neither the formal displays nor the exaggerations of colour and ornament which so commonly accompany them, are due to female choice; a choice not necessarily conscious, but rather to be interpreted as the final abandonment to the finest performer of a number of suitors. On the contrary, this ornamentation, of whatever kind, is the expression of an intensification of the gland secretions which is manifested by the process of pigment concentration and a consequent intensification of coloration. Hand in hand with these developments it would appear goes an exaggeration of the normal movements which characterize the species when under the influence of great excitement, whether of fear or pleasure. At any rate, the displays of gaudily coloured and highly ornamental species are commonly more striking than those of sober hue. On this rendering, the behaviour of Reptiles, Amphibia and Fishes, is much more readily interpreted, and this is even truer of the more lowly groups of animals such as Spiders, Butterflies and Beetles. Among the Reptiles, as among the birds and beasts, the desire to obtain territory seems to be strong. But the information to be gathered as to their behaviour in the search for mates, and after, is exceedingly small. Sluggish by nature, all become animated under the stimulus of mate-hunger, and this is especially true of the males. As one would have expected, from what has just been said, desire is most demonstrative in brightly coloured and highly ornamented species. But even the dullest hued and most phlegmatic display quite surprising agility and animation under the fever of Love. Thus among the Crocodiles fierce battles are fought by rival males for the possession of some coveted female: and later the victor strives to dispel the apathy of his mate by caperings most undignified in a Crocodile. He will twist and turn, or rather twirl, round on the surface of his chosen pool, with head and tail raised high in air, and his capacious barrel of a body swollen out to bursting point. These antics are performed to the accompaniment of loud bellowings and roars heard at no other season of the year. But more than this, an appeal is made to the nose as well as to the eyes of his apathetic mate, for during all this parade of love he exudes from glands in the lower jaw, and tail, an almost overpowering smell of musk. At last, however, these antics have their reward, for sooner or later apathy awakens into interest, and interest ends in desire.