760 REPORT—1899. 
foliage, flowers, and tubers of the Magnum Bonum variety ; if it be of the Snowdrop, 
the toliage, flowers, habit, and tubers are totally different from the Magnum 
Bonum, and are easily identified as Snowdrops. In this way a favourable variety 
of potato can be reproduced to almost any extent with all its peculiarities of earli- 
ness or lateness, pastiness or mealiness, power of resisting disease, and so forth. 
By asexual reproduction the exact facsimile of the parent may always be obtained, 
provided the conditions remain the same. 
Now let us turn to the results of sexual reproduction—the seeds, 7.e. the real 
seeds, which as you know are produced in the flowers, are the means by which 
sexual reproduction is effected. They are produced in great quantity by most 
plants, and when placed in the ground under the proper conditions they germinate 
and produce plants. But these plants do not resemble the parent. Try the seed 
of the Magnum Bonum potato, and raise plants from it. Do you think that any of 
them will be the Magnum Bonum with all its properties of keeping, resisting dis- 
ease, and so forth? Nota bit of it. The probability is, that not one of your 
seedling plants will exactly reproduce the parents; they will all be different. 
Again, take the apple; if you sow the seed of the Blenheim Orange and raise 
young apple-trees, you will not get a Blenheim Orange. All your plants will be 
different, and probably not one will give you apples with the peculiar excellence of 
the parent. If you want to propagate your Blenheim Orange and increase the 
number of your trees, you must proceed by grafting or by striking cuttings, which 
are the methods by which such a tree may be asexually reproduced. And so on. 
Examples might be multiplied indefinitely. Every horticulturist knows that 
variety characterises seedlings, 7.c. sexual offspring, whereas identity is found in 
slips, grafts, and offsets, z.c. in asexual offspring; and that if you want to get a 
new plant you must sow seeds, while if you want to increase your stock of an 
old one you must strike cuttings, plant tubers, or proceed in some analogous 
manner, 
An apparent exception to this rule is afforded by so-called bud variation, but 
it is not certain that this is really an exception. In so far as these bud variations 
are not of the nature of acquired variations produced by a change of external con- 
ditions, and disappearing as soon as the old conditions are renewed, they are pro- 
bably stages in the growth and development of the organism. That is to say, they 
are of the same nature as those peculiarities in animals which appear at a particu- 
lar time of life, such asa single lock of hair of a different colour from the rest of the 
hair,’ the change in colour of hair with growth,” the appearance of insanity or of 
epilepsy at a particular age. There is nothing more remarkable in a single bud on 
a tree departing from the usual character at a particular time of life, than in a 
particular hair of a mammal doing the same thing. 
We have seen that, speaking broadly, genetic variation is connected with sexual 
reproduction, and it becomes necessary to examine this mode of reproduction a 
little more fully. What is the essence of sexual reproduction, and how does it 
differ from asexual? What I am now going to say applies generally to the 
phenomenon whether it occurs in plants or animals. Sexual reproduction is 
generally carried on by the co-operation of two distinct individuals—these are 
called the male and female respectively. They produce, by a process of unequal 
fission which takes place at a part of their body called the reproductive gland, a 
small living organism called the reproductive cell. The reproductive cell produced 
by the male is called in animals the spermatozoon, and is different in form from 
the corresponding cell produced by the female, and called in animals the ovum. 
The object with which these two organisms are produced is to fuse with 
one another and give rise to one resultant uninucleated organism or cell, 
which we may call the zygote. This process of fusion between the two kinds 
of reproductive cells, which are termed gametes, is called conjugation, The 
difference in structure between the male and female gamete is a matter of 
secondary importance only, and is connected with the primary function of 
1 Darwin, Vasiation, vol. i. p. 449. ; 
2 As an example I may refer to the Himalayan rabbit; Darwin, Variation, 
vol, i, p. 114, 
