558 MERISTIC VARIATION. [part i. 



One further point remains to be spoken of. We have said 

 that a system of parts in Secondary Symmetry is in a sense 

 analogous with a bud, but in one respect the condition of these 

 parts differs remarkably from all phenomena of budding or 

 reproduction that are seen elsewhere. In a bud the various 

 organs always present the same surfaces to each other, or in 

 other words, the planes of division always pass between similar 

 surfaces. In Secondary Symmetries this is not the case. As 

 illustrated by the diagram on p. 481, the extra parts may present 

 to each other, or remain compounded by any of their surfaces, 

 whether anterior, posterior, or otherwise. This seems to be 

 altogether unlike anything ever met with in animals and plants. 

 It is as if in a bud on a plant two leaves on opposite sides of the 

 axis could in their origin indifferently present any of their surfaces 

 to each other. 



It will be remembered that the symmetry cannot be the result 

 of subsequent shiftings, but must represent the original manner of 

 cleavage of the two extra limbs from each other. We must there- 

 fore conceive that in the developing rudiment of the two extra 

 limbs either surface may indifferently be external, the polarity 

 being ultimately determined by the relation of the bud or 

 rudiment to the limb which bears it. 



