night-blind male and female. Otherwise the same as for L 1.
Pedigrees of hereditary congenital Nystagmus (involuntary rhythmical movements of the eyes) showing two different modes of descent.
In Figure L 3a the nystagmus occurs only in males and descends through unaffected females.
In Fig. L 3b both males and females are liable to the disease, and either parent may transmit it, although descent is more often through mother than father.
The movements of the eyes are very often accompanied by rhythmical movements of the head in the non-sex-limited type (Fig. L 3b), but head movements very seldom occur in the male-limited type (Fig. L 3a).
In both types many of those affected have also optical defects of the eyes, especially astigmatism. No mental or nerve complications in either kind.