found amongst the surface-swimming Ascidians of the sea--the
glass-like Salps. But our common ferns and mosses also show this same
alternation of sexual and sexless generations, the two generations
differing greatly in size, form, and structure from one another,
whilst the whole story of "flowers" and their structure is bound up
with a wonderful "telescoping" or rolling of the two generations
(sexless and sexual) into one plant!

It was not until long after Harvey's time that these things were
understood, and there was every excuse--in the absence of observation
of the facts, especially those yet to be revealed by the
microscope--for the erroneous suppositions and explanations which were
formerly entertained as to the mode of reproduction of the less
familiar plants and animals. If we go back to the starting-point of
European science, to the great Aristotle, we find that he had formed
singularly correct conclusions as to the reproduction of the larger
kinds of animals, though he knew nothing about "sperms," having no
microscope, and only regarded the fluid produced by male animals as
exercising a fertilising effect on the eggs, which in many instances
are large enough for anyone to see. But, of course, he could not have
any knowledge of the egg-cell, nor does he say anything about the
reproduction of plants. Later, however, the sexuality of flowering
plants was taught by his pupils, and at the time of the Roman Empire
there was a very definite belief among learned men (such as Pliny)
that the larger plants and animals reproduce by eggs or by seeds
produced by the females which require to be "fertilised" by a product
formed in the males--the spermatic fluid in the case of animals and by
the pollen in the case of a few flowering plants (_e.g._ the
date-palm). But there was no idea of holding this as a general and
universal law. From Pliny to Harvey and later, those who concerned
themselves with natural history accepted without difficulty any
strange accounts or appearances as to the reproduction or the sudden
production in fanciful and astonishing ways of the lower and smaller
animals and plants. They did not expect these inferior creatures to
have the same methods of reproduction as the higher and bigger
creatures. It is only now, since the later years of the nineteenth
century, that we are able to show that all animals and plants, even
the minutest microscopic kinds, reproduce by the formation and
separation of egg-cel