be maintains that this "organic growth" does not always 

 aim at perfection but often tends to simplification and ret- 

 rogression. 



The following, then, according to Eimer, are the di- 

 rective principles of variation: (i). The general law of 

 coloration (stripes running lengthwise change into spots, 

 stripes running crosswise change to a uniform color). (2). 

 The law of definitely directed local change (new colors 

 spread from the rear to the front and from above down- 

 ward or vice versa, old colors disappear in the same direc- 

 tions. (3). The law of male predominance (males are as a 

 rule one step in advance of the females in develo.pment). 

 Female predominance is an exception. (4). The law ofi 

 age-predominance (new characters appear at a well-ad- 

 vanced age, and at the time of greatest strength). (5. The 

 law of wave-like development (during the course of the 

 formation of the individual organism a series of changes 

 proceed in a definite direction over the body of the ani- 

 mals). (6). The lawi of independent uniformity of devel- 

 opment (the same course of development is pursued in 

 non-related forms and results in similar forms). (7). The 

 law of development through different stages (different 

 characteristics of the same being may develop to a different 

 degree and in different directions). (8). The law of uni- 

 lateral development (the progeny does not present a com- 

 plete combination of the characters of the parents but 

 manifests a preponderance of the characteristics of either 

 parent). (9). The law of the reversal of development (the 

 direction of develpoment may reverse and tend towards the 



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