ENTOMOLOGICAL NEWS. 



PHILADELPHIA, PA., APRIL, 1915. 



The Intensive Study of Species. 



The differentiation of species or of larger taxonomic 

 groups on the basis of the differences shown by a single 

 structural feature, a single organ or a single system of organs, 

 is a familiar feature in the history of biological classification. 

 As a student of the late Prof. E. D. Cope, we recall a remark 

 made by him to the effect that eventually each group would 

 probably be defined by a single character only. At nearly the 

 same time, Dr. George H. Horn would express his belief that 

 the study of a hitherto unregarded organ in any series of 

 living things would ultimately improve and correct the tax- 

 onomy of that same series as previously established on other 

 characters. 



Recent tendencies seem to incline to Horn's view rather 

 than to Cope's. Prof. Castle has expressed these tendencies 

 thus: 



If we compare one wild species with another, we commonly find 

 existing between them not single striking differences but numberless 

 minute differences if one makes an intensive study of related spe- 

 cies, he finds that they differ in endless details of structure and physio- 

 logical behavior extending even to differences in size of the constituent 

 cells of the body (Conklin), or of their parts (chromosomes, chromo- 

 meres, etc.). (Science, Jan. 15, 1915, p. 96.) 



Prof. McClung tells us of having corrected a false label on 

 a microscopic slide of sections of a grasshopper's testis by 

 recognizing the differences in the chromosomes of the species 

 really present and of that which it purported to be. 



In a recent obituary of Prof. C. S. Minot we have quoted 

 his conclusion "even a piece of cuticle suffices for the identifi- 

 cation of the species" of a Lepidopterous larva. 



The minuter differences, the finer discriminations, these are 

 the signs of the times in taxonomy and Prof. Castle, in the 

 article from which our quotation is made, shows in a most 

 interesting way how these small differences are related to the 

 possibilities in evolution. 



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