SPECIES. 257 



have a growth, a youth, a mature age, an old age, and are 

 bound to some limited home during their lifetime. It is 

 true that species are also limited in their existence; but 

 for our purpose we can consider these limits as boundless, 

 inasmuch as we have no means of fixing their duration, 

 either for the past geological ages or for the present 

 period, whilst the short cycles of the life of individuals 

 are quantities easily measurable. Now, as truly as indi- 

 viduals, while they exist, represent their species for the 

 time being and do not constitute them, so truly do these 

 same individuals represent at the same time their genus, 

 their family, their order, their class, and their type, the 

 characters of which they bear as indelibly as those of the 

 species. 



As representatives of Species, individual animals bear 

 the closest relations to one another; they exhibit definite 

 relations also to the surrounding elements, and their ex- 

 istence is limited within a definite period. 



As representatives of Genera, these same individuals 

 have a definite and specific ultimate structure, identical 

 with that of the representatives of other species. 



As representatives of Families, these same individuals 

 have a definite figure, exhibiting, with similar forms of 

 other genera, or for themselves, if the family contains but 

 one genus, a distinct, specific pattern. 



As representatives of Orders, these same individuals 

 stand in a definite rank when compared to the representa- 

 tives of other families. 



As representatives of Classes, these same individuals 

 exhibit the plan of structure of their respective types in 

 a special manner, carried out with special means and in 

 special ways. 



As representatives of Branches, these same individuals 



