ls, and that these egg-cells are (in all but a
few exceptional cases) fertilised by sperm cells, which are smaller
than the egg-cells, and usually provided with active swimming
filaments.

Not only did our mediaeval ancestors believe all sorts of fancies as to
the propagation of lower animals and plants, but they were quite
prepared to accept stories as to reproduction in the case of higher
animals, and even in mankind, by irregular methods, such as
parthenogenesis, or the defect of an ordinary male parent. In the
Middle Ages in Europe, and earlier in the East, the belief in the
frequent occurrence of the birth of a child which had no human male
parent was common. It was, so to speak, an admitted though irregular
occurrence. A very curious thing is that when such cases were supposed
to occur, they were not ascribed to any natural process such as we now
recognise in the "parthenogenesis" of insects and crustaceans, but to
the visitation of the mother by a spirit--a floating, volatile demon
or angel (known as an "incubus" in the Middle Ages) beneficent or
malicious as the case might be. Stories of the nocturnal visits of
these mysterious ghostly "incubi" are on record in great number and
variety, both in European and Oriental tradition and legend. There
seems to have been a readiness to believe the theory of paternity from
among the hidden world of goblins, fairies, and sprites which was very
naturally made use of by a woman and her relatives when she could not
produce the father of her child.

We come across examples of such beliefs in invisible agents of
paternity even among the more cultivated Romans. Thus Virgil in his
"Georgics" cites as a fact that mares are fertilised by the wind. His
words are given on the next page.

It is now known that, quite apart from any motive of concealment of
the true paternity of their offspring, some of the native tribes of
Australia have the belief that, as the regular and normal thing,
children are begotten by strange fairy-like spirits which haunt the
rocks and trees of certain localities and enter the future mother as
she passes by these haunted rocks and trees. These Australian "black
fellows" hold that the human father counts for nothing in the matter.
The belief of these Australian savages is referred to by writers on
the subject (Mr. Andrew Lang and others) as "the spiritual theory of
conception." There are some reasons for thinking that this curious
theory and the accompany