CONJUGATION ^ SEXUAL REPRODUCTION. 45 



We may illustrate the cycle of metazoan animals thus : — 

 i Sexual Reproduction (fusion of nuclear material ).k 



A/ 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 :- 



CONIUGATION. SEXUAL REPRODUCTION. 



A preparatory process, con- 

 sisting of reduction of the 

 nuclear material by divisions 

 of the nuclei only. 



Mutual interchange of nuclear 

 material between the two 

 individuals, and fusion of 

 the respective nuclei. 



Separation of the two individ- 

 uals, followed by growth and 

 binary fission to form many 

 unicellular individuals. 



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 all 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. 



