54 BIOLOGY 



CHAPTER X 



REPRODUCTION 



THERE are two distinct phases in the life of every 

 organism which we may name the individual and the 

 reproductive : the first, during which the whole energy 

 of the organism is devoted to its own advantage, the 

 second, in which organs come into play whose activity 

 causes a great drain on the resources of the organism, 

 as they are unable to provide for themselves. Moreover 

 the offspring among the- higher forms are, for a varying 

 period, dependent on the parent for nourishment. Thus 

 we see that nature is apt to be careless of the individual 

 life in her endeavours to be careful of the species. 



At some period in the life-history of every plant and 

 animal, provision is made for the continuance of the 

 species, and this may be made in one or occasionally in 

 both of two ways : either by the separation of some 

 part of the body which can develop directly into a new 

 organism of the same kind, or by the separation of a 

 cell the ovum or egg-cell which in itself is incapable 

 of further development, save in exceptional cases, with- 

 out previous fusion with another [cell the sperm cell 

 which is usually in animals, and very frequently in 

 plants, derived from another individual. 



Among the lower forms of living organisms, growth 

 is regularly followed by fission or by budding, but as 



