transmitted from the father to his sons and grandsons alone; so it has been
with other cases of ichthyosis, with supernumerary digits, with a deficiency
of digits and phalanges, and in a lesser degree with various diseases,
especially with colour-blindness and the haemorrhagic diathesis, that is, an
extreme liability to profuse and uncontrollable bleeding from trifling wounds.
On the other hand, mothers have transmitted, during several generations, to
their daughters alone, supernumerary and deficient digits, colour-blindness
and other peculiarities. So that the very same peculiarity may become attached
to either sex, and be long inherited by that sex alone; but the attachment in
certain cases is much more frequent to one than the other sex. The same
peculiarities also may be promiscuously transmitted to either sex. Dr. Lucas
gives other cases, showing that the male occasionally transmits his
peculiarities to his daughters alone, and the mother to her sons alone; but
even in this case we see that inheritance is to a certain extent, though
inversely, regulated by sex. Dr. Lucas, after weighing the whole evidence,
comes to the conclusion that every peculiarity tends to be transmitted in a
greater or lesser degree to that sex in which it first appears. But a more
definite rule, as I have elsewhere shown (14/26. 'Descent of Man' 2nd edition
page 32.) generally holds good, namely, that variations which first appear in
either sex at a late period of life, when the reproductive functions are
active, tend to be developed in that sex alone; whilst variations which first
appear early in life in either sex are commonly transmitted to both sexes. I
am, however, far from supposing that this is the sole determining cause.

A few details from the many cases collected by Mr. Sedgwick (14/27. On Sexual
Limitation in Hereditary Diseases 'Brit. and For. Med.-Chirurg. Review' April
1861 page 477; July page 198; April 1863 page 445; and July page 159. Also in
1867 'On the influence of Age in Hereditary Disease.'), may be here given.
Colour-blindness, from some unknown cause, shows itself much oftener in males
than in females; in upwards of two hundred cases collected by Mr. Sedgwick,