REPRODUCTION. 5 



loss of precedence in life that favours some antagonistic 

 force, whose predominance results in premature death, we 

 know, without at the same time being able to give a satis- 

 factory explanation of all the concurrent phenomena, that 

 under prevailing conditions there is a limit to the existence 

 of every living organism, that can be predicted within mea- 

 surable limits. Under normal conditions, before this period 

 arrives, certain portions of the living organism possessing 

 all its vital properties have become specialized, and even- 

 tually separate from the parent form ; such bodies in 

 the vegetable kingdom are known in the broader sense as 

 seeds or reproductive bodies. Leaving out of consideration 

 for the present certain transition forms and complications, 

 the germination of a seed is considered as the commence- 

 ment of a new individual of the same species or kind as its 

 parent or the individual that produced it. The idea of an 

 individual as defined above is a convenient one, if at the 

 same time we clearly realize the actual condition of things. 

 There is not the slightest reason for believing in so-called 

 spontaneous generation ; in other words, in the conversion of 

 inorganic matter into a living organism by any other agency 

 than that exercised by a previously existing form of life ; 

 hence we are constrained to assume the existence of a parent 

 form as the progenitor of every living organism that exists 

 at the present day. At the same time it is well known that 

 plants and animals vary in their structure and habits to a 

 greater or less extent from time to time, consequently it is 

 not necessary to assume that all the progenitors of any given 

 plant existing at the present time were in all respects similar 

 to the latest product. In speaking of a seed as the com- 

 mencement of a new individual, we do so only in a restricted 

 sense, remembering the fact that the seed once formed an 



