DEGENERA TION. 2 7 



possessors greater powers, enabling them to cope 

 more successfully with others in that struggle for 

 existence in virtue of which these new organs 

 have been little by little called into being. At the 

 same time here and there along the line of march, 

 certain forms have been supposed to have '' fallen 

 out," to have ceased to improve, and being happily 

 fitted to the conditions of life in which they were 

 long ago existing, have continued down to the 

 present day to exist in the same low, imperfect 

 condition. It is in this way that the lowest forms 

 of animal life at present existing are usually 

 explained, such as the microscopic animalcules, 

 Amoebse and Infusoria, It is in this way that the 

 lower or more simply-made families of higher groups 

 have been generally regarded. The simpler living 

 Mollusca or shellfish have been supposed necessarily 

 to represent the original forms of the great race of 

 Mollusca. The simpler Vertebrates have been sup- 

 posed necessarily to represent the original Verte- 

 brates. The simpler Worms have been supposed 

 necessarily to be the stereotyped representatives of 

 very ancient Worms. 



That this is, to a certain extent, a true explanation of 



