These examples of hermaphrodite love lead us forward to a further step, where no reproduction takes place without the special activity and conjugation of two kinds of specialised cells, and these two kinds are carried about by separate individuals. In some species--fishes, for example--the two kinds of special cells meet outside the bodies of the parents. At this humble level the sexes are in many cases very like one another, and there is, as we should expect, a good deal of haphazard in the production of offspring. Among fishes, for instance, the eggs and sperms are liberated into the sea, or the shallow bed of a river, and, if the sperms (the milt of the males) are placed near to the spot where the eggs (the spawn) have been laid, fertilisation occurs, for within a short distance the sperms are attracted--in a way that is imperfectly understood--to enter the eggs. By this method there is of necessity great waste in the production of offspring, many thousands of eggs are never fertilised. The union of the sexual cells must be something more than haphazard for further development. There must be some reason inherent in the female or male inducing to the act of reproduction. In other words, there must be a psychic interest preceding the sex act. In this way a higher grade is reached when the presence of one sex attracts the other. Gradually the female and the male begin to associate in pairs. We may illustrate this important step in the evolution of love by reference to the familiar case of the salmon. The male courts the female and is her attendant during the breeding season, fertilising the deposited ova in her presence. He guards her from the attention of all other males, fighting all rivals fiercely, with a special weapon, developed at this time, in the form of a hooked lower jaw with teeth often more than half-an-inch long. Darwin records a case, told to him by a river-keeper, where he found three hundred dead male salmon, all killed through battle.[44] Thus even among cold-blooded fishes (though it may appear folly to use the word "love" in this connection) a very clear likeness with our human sex-passions can be traced.