The combinations just given represent the possible offspring from a pair of hybrid parents. If we look them over, we see at once that only half of them are hybrid, namely, combinations ABCabc and abcABC; the other half are pure breed, the chromosome pairs being exactly alike; but these pure breeds are of two kinds, one having only large-letter determiners, the other only small-letter. If it is a case where the large letters dominate over the small, the large letter pure breeds and the hybrids will look alike, but the small-letter pure breeds will look different, since in them the traits governed by the small-letter determiners have a chance to show themselves. A very good illustration of this is seen in eye color in human beings. Brown eyes are dominant over blue; in other words, the determiner that causes eyes to be brown dominates over that responsible for blueness in cases where both come together in hybrids. A person who has brown eyes may be either a pure breed in that respect or may be a hybrid; there is no way to tell the difference from the appearance; but if the brown-eyed person has offspring, and any of them turn up with blue eyes, it is proof positive that the parent is a hybrid so far as eye color is concerned. Moreover, the blue-eyed child is not a hybrid in this respect; his brown-eyed brethren may or may not be; in the long run two-thirds of them will prove so; the other third will be pure breed, having in their chromosome pairs only brown-eye determiners. Where the hybrids differ from the pure breeds, as in the case of the four-o’clocks, given earlier, it is easy, of course, to tell which are pure and which are hybrid. When pink four-o’clocks are interbred, the chromosomes will combine just as described above for hybrids, since the plants that have pink flowers are hybrid. One-half the offspring will have pink flowers, showing that they are hybrid; one-fourth will have white flowers, proving that in them the white-flower determiners have separated out, and the other fourth will have red flowers, because in them the red-flower determiners are the only kind present. This and similar experiments have been tried hundreds of times, and whenever the numbers of offspring have been great enough to allow the chances to equalize, the proportion of different kinds of offspring has always agreed almost exactly with expectation. Of course in human beings the families are not large enough for this always to work out accurately, but even so the agreement is often striking. [Illustration: CARING FOR THE BABY’S EARS Important for adults and babies alike] [Illustration: THE BABY’S FOOTPRINT A means of positive identification] [Illustration: BABIES PHYSICALLY AND MENTALLY ACTIVE]