446 SUMMARY. 



close resemblance in the individual embryo of the parts 

 which are homologous, and which when matured become 

 widely different in structure and function ; and the resem- 

 blance of the homologous parts or organs in allied though 

 distinct species, though fitted in the adult state for habits as 

 different as is possible. Larvae are active embryos, which 

 have been specially modified in a greater or less degree in 

 relation to their habits of life, with their modifications in- 

 herited at a corresponding early age. On these same prin- 

 ciples, and bearing in mind that when organs are reduced in 

 size, either from disuse or through natural selection, it will 

 generally be at that period of life when the being has to 

 provide for its own wants, and bearing in mind how strong 

 is the force of inheritance — the occurrence of rudimentary, 

 organs might even have been anticipated. The importance 

 of embryological characters and of rudimentary organs in 

 classification is intelligible, on the view that a natural 

 arrangement must be genealogical. 



Finally, the several classes of facts which have been con- 

 sidered in this chapter, seem to me to proclaim so plainly,' 

 that the innumerable species, genera, and families, with 

 which this world is peopled, are all descended, each within 

 its own class or group, from common parents, and have all 

 been modified in the course of descent, that I should with- 

 out hesitation adopt this view, even if it were unsupported 

 by other facts or arguments. 



