CONJUGATION & SEXUAL REPRODUCTION. 45 
We may illustrate the cycle of metazoan animals thus :— 
Sexual Reproduction (fusion of nuclear material ). 
Series of cell-divisions. Alternation of growth and, 
binary fission producing a single multicellular 
individual. 
If we compare this with the cycle of protozoan animals 
(page 40), the relation of conjugation to sexual reproduction 
becomes clear. 
We may tabulate the two phenomena as follows :— 
CONJUGATION. 
1. A preparatory process, con- 
sisting of reduction of the 
nuclear material by divisions 
of the nuclei only. 
2. Mutual interchange of nuclear 
material between the two 
individuals, and fusion of 
the respective nuclei. 
3. Separation of the two individ- 
uals, followed by growth and 
binary fission to form many 
unicellular individuals. 
SEXUAL REPRODUCTION. 
1. Maturation of sexual ele- 
ments, consisting of reduc- 
tion of nuclear material by 
divisions of nuclei and cells. 
2. Fertilisation, consisting of the 
passage of a/7 male element 
over to the female element, 
and the fusion of the two. 
3. Division of fertilised ovum by 
growth and binary fission to 
form one multicellular indi- 
vidual. 
