facts which we only rediscovered between 1830 and 1860. It is certain,
for instance, that he was acquainted with the very peculiar mode of
propagation of the cuttlefishes, or cephalopods, in which a yelk-sac
hangs out of the mouth of the foetus. He knew, also, that embryos come
from the eggs of the bee even when they have not been fertilised. This
"parthenogenesis" (or virgin-birth) of the bees has only been
established in our time by the distinguished zoologist of Munich,
Siebold. He discovered that male bees come from the unfertilised, and
female bees only from the fertilised, eggs. Aristotle further states
that some kinds of fishes (of the genus serranus) are hermaphrodites,
each individual having both male and female organs and being able to
fertilise itself; this, also, has been recently confirmed. He knew
that the embryo of many fishes of the shark family is attached to the
mother's body by a sort of placenta, or nutritive organ very rich in
blood; apart from these, such an arrangement is only found among the
higher mammals and man. This placenta of the shark was looked upon as
legendary for a long time, until Johannes Muller proved it to be a
fact in 1839. Thus a number of remarkable discoveries were found in
Aristotle's embryological work, proving a very good acquaintance of
the great scientist--possibly helped by his predecessors--with the
facts of ontogeny, and a great advance upon succeeding generations in
this respect.

In the case of most of these discoveries he did not merely describe
the fact, but added a number of observations on its significance. Some
of these theoretical remarks are of particular interest, because they
show a correct appreciation of the nature of the embryonic processes.
He conceives the development of the individual as a new formation, in
the course of which the various parts of the body take shape
successively. When the human or animal frame is developed in the