THE NATURE OF SPECIES 



PouLTON, E. B. President's Address. "What is a Species?" Trans. 

 Entom. Soc. London, pp. Ixxvii-cxvi. 1903. 



RowE, A. W. An Analysis of the Genus Micraster, as Determined 

 by Rigid Zonal Collecting from the Zone of Rhynconella 

 cuv'tert to that of Micraster cor-angu'tmim. Quart. Jour. Geol. 

 Soc, Vol. LV, pp. 494-547, pi. 35-39. 



Spencer, Herbert. The Development Hypothesis. Reprinted in 

 Essays — Scientific, Political, and Speculative, I, 1868, 1854. 



The Conception of Species. A discussion at the British Asso- 

 ciation, Oxford, 1926. Rep. Brit. Assoc, 1926, pp. 356-357. 



"All students were so impressed with the belief in the reality and per- 

 manence of species that endless labour was bestowed on the attempt to 

 distinguish them — a task whose hopelessness may be inferred from the fact 

 that even in the well-known British flora one authority describes sixty-two 

 species of brambles and roses and another of equal eminence only two species 

 of the same group." — A. R. Wallace. 



"A species is supposed to be a group of individuals that closely resemble 

 one another owing to their descent from common ancestors — a group that 

 has become more or less sharply separated from all other coexisting species 

 by the disappearance of intermediate forms." "The more we study the 

 animal and vegetable kingdoms . . . the more clearly is the fact impressed 

 upon us that if we could have before us all past and present individuals 

 we should find it impossible, except in an arbitrary manner, to arrange 

 them in species at all, for each kind would be found to be connected with 

 others by series of small gradations." — Arthur Dendy, Outlines of Evolu- 

 tionary Biology. 



"The question what constitutes a species must be left to the judgment 

 or fancy of the individual." — H. S. Jennings. 



Modern students of nature do not find, as Linnaeus stated about two 

 hundred and fifty years ago: "There are as many diflFerent species of animals 

 and plants on earth as there were different forms created in the beginning." 



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