THE COURTSHIP OF ANIMALS relation to the mind of the opposite sex; that mind has thus been the sieve through which variations in courtship characters must pass if they are to survive, Down at the base of the animal scale courtship of course does not exist. Jellyfish or sponges or sea-urchins simply shed their repro- ductive cells into the water and trust to luck for fertilization. It is only when male and female must actually co-operate for fertilization to be effected, that we can expect to find courtship; and even so it will not exist unless there is a fairly elaborate brain and nervous system. Perhaps the first adumbration of courtship is seen in the nuptial dances of certain marine bristle-worms (Polychaetes), in which at certain seasons of the year and phases of the moon the creatures swim up out of their crannies in the rocks and gather in groups, excited males wriggling round the females. It is possible that the presence of the dancing males in some way stimulates the females to lay their eggs, upon which the male elements are discharged in milky clouds. Snails too have a primitive courtship, which is complicated by the fact that they are bi-sexual and each in its role of male attempts to stimulate the other in its r61e of female. But the first actions to which the name courtship., and not merely perhaps direct stimulus to fertilization, must be given are those of a few crabs and most spiders. Among the crustaceans, the fiddler-crab is characterized by the presence in the male of one enormously en- larged claw, which may weigh almost as much as the rest of the body, and is often brightly coloured. It used to be supposed that with this the males stopped tlieir burrows, or fought other males, or seized and carried off the females. However, the careful studies of Dr Pearce show that its main function is one of display. In the mating season, when a female comes past, the males throw themselves into a tip-toe attitude, with big claw rigidly held aloft. If the female takes no notice, the male runs again to where she can see him, and again strikes the statuesque pose: if she goes too far, he returns to his burrow. The observer summed up his impressions thus: " One could only say that the males appeared to be displaying their maleness." There we have the clue to the origins of courtship in a nutshell. Once the brain reaches a certain complexity, it controls behaviour. A crab can react to various situations—a food-situation, a hunger- situation, a fear-situation, a sex-situation; and the statuesque male with his uplifted claw is the sign and symbol of the sex-situation, just as the coming of a man or other large animal among the burrows constitutes an enemy-situation, with resultant scuttling. Doubtless even without such male advertisement, mating would eventually 8?