308 I The Process of Evolution 



of that in all animals. We greatly need studies of patterns of diflPer- 

 entiation in all groups. These studies must be made with sampHng 

 and analyses designed to describe the patterns present regardless of 

 their configurations, not to apportion the variation into prepared 

 compartments. The protestations of taxonomists, especially those 

 working with vertebrates, that they almost always find "good" spe- 

 cies must be discounted. Their methods and attitudes tend to ex- 

 clude all other possibilities. For instance, as D. A. West pointed 

 out in his interesting paper on grosbeak hybridization, "[hybrid] 

 specimens are often labeled as one or the other species and are thus 

 buried unreported in collections." 



When more objective analyses have been completed, it may be 

 discovered that the process of differentiation of populations is more 

 complex than commonly supposed. If this is the case, the splitting 

 part of the evolutionary process can be given much closer scrutiny. 



More objective and quantitative methods of describing relation- 

 ships will also be of aid in the study of the evolution of develop- 

 mental systems. Can the larvae and adults of holometabolous in- 

 sects evolve semi-independently? Can the gametophytic and spo- 

 rophytic generations of the same plant follow different evolutionary 

 pathways? If so, one could expect two separate numerical taxonomic 

 studies, one based on adult characters and the other based on larval 

 characters, to give systems of relationship that were not entirely 

 congruent. At least one recent study comparing adult and larval 

 mosquitoes has shown some discordance. It is all too common to 

 think of evolution as operating on adult forms only, whereas actually 

 the entire course of development is under selective control. The study 

 of interactions of evolutionary pressures at various stages of develop- 

 ment has barely been started. 



In this section, the so-called species problem has been used as 

 representative of a whole class of problems because it has held great 

 interest (often mainly practical) for most evolutionists. Ideas such as 

 niche, community, and climax, which are ecological concepts having 

 much in common with the biological species, could be similarly 

 treated. Further discussion of these may be found in references 

 listed in Ehrlich and Holm (1962). 



EVOLUTIONARY BIOLOGY 



In the past two centuries, few, if any, scientific ideas have been sub- 

 jected to as many vicissitudes as the idea of evolution through 

 natural selection. The theory was violently opposed by many clergy- 

 men when it was first proposed by Darwin and is still anathema to 



