192 APPENDIX II INTENSIVE SEGREGATION. 



(7) Amalgamational intension, or segregation and divergence 

 through independent amalgamation. 



(8) Fecundal intension, or segregation and divergence through 

 independent fecundal transformation. 



In groups that do not intergenerate, divergent forces reveal them- 

 selves whenever transformation is introduced. If it were possible to 

 believe that the effects of independent selection or of independent 

 suetude had been completely parallel, it would still be impossible to 

 believe that both of these, together with the remaining six principles 

 of transformation, would ever so combine as to produce completely 

 parallel transformation in isolated sections of a species, even if all 

 were surrounded by the same environment. This principle is not 

 inconsistent with the introduction of what Professor Hyatt calls 

 "representative of parallel characteristics" in two or more divergent 

 series of forms. What he points out is that, under the influence of 

 heredity, similar organisms exposed to similar environments undergo 

 similar transformation (Anniversary Memoirs of the Boston Society 

 of Natural History, 1880: "The Genesis] of the Tertiary Species of 

 Planorbis at Steinheim," pp. 24-29). 



In the description of these principles I have used the adjective 

 "independent" to signify that the principle is operating in sections 

 of the species that are prevented from intergenerating. In the term 

 "independent variation" Mr. Romanes has already used the adjec- 

 tive "independent " as meaning "when accompanied with the prevention 

 of intercrossing." 



6. The Pervasive Influence of the Causes of Transformation and the 



Law of Intension. 



In my paper on " Divergent Evolution " I made the statement that 

 ' ' When separate generation is long continued we have reason to believe 

 it always passes into segregate generation with divergent evolution." 

 The same thought had been expressed in a previous paper by the 

 statement that ' ' Variation is so strong that all that is necessary to 

 secure divergence of types is to prevent their intermingling."* The 

 certainty that independent generation with transformation will never 

 produce parallel, but always more or less divergent evolution is the law 

 of intensive segregation already referred to. But in addition to this cer- 

 tainty there is a very strong probability that where independent gen- 

 eration is long continued, transformation of some kind will supervene. 

 If there are any species in which the power of cumulative variation has 



* See "Diversity of Evolution under One Set of External Conditions." Journ. 

 Linn. Soc., Zool., vol. xi, p. 499. 



