APPENDIX. 
123 
Of course the best-known method of reproduction of organisms 
is sexual reproduction— that is, by the union of two germs ; but 
1 need not tell you who are familiar with such things as buds, 
bulbils, and cuttings that there are asexual modes of reproduction! 
Diagram of the fertilisation of the egg in Ascarls megalocephala . — 
(Compounded from the figures and descriptions of Boveri and others.) 
I. — The sperm-cell ( sp ) is about to enter the ovum, which contains a nucleus (nov) 
and centrosome (cs). Rk I and Rk II — the two primary polar-bodies, the first 
of which has divided into two ; each contains two idants. 
II. — The sperm-nucleus ( nsp ) has passed into the egg, near the nucleus of which 
it is situated. Each of these nuclei contains two idants, and also a centro- 
some, which has divided into two. 
III. — The two nuclei are now close together : the centrosomes, with their 1 spheres 
of attraction,’ are connected together in pairs, and are situated at the poles of 
the spindle, which is already visible. 
IV. — The nuclear membrane has disappeared, and the first embryonic nuclear 
division is now taking place. 
Of these, in the animal kingdom, I may mention the partheno- 
genetic production of drone eggs by the queen bee, and the 
viviparous reproduction of aphides, or green fly, by the imperfect 
insect, both of which are quite independent of any process of 
fertilisation. You will not be astonished, therefore, if 1 tell you 
