PART V 



ATTEMPT AT A CLASSIFICATION OF THE 

 PRIMORDIA 



§52. — PRELIMINARY REMARK: NUMEROUS PRI- 

 MORDIA ARE MENTIONED IN THE EXISTING DESCRIP- 

 TIVE LITERATURE.— When we intend to apply the quanti- 

 tative method to the study of any species, we must first of all 

 discover a certain number of its priraordia. Very often we 

 find the wanted information, at least to a considerable extent, 

 by consulting a fliora or a fauna in which the species is described. 

 The amount of material accumulated in descriptive literature 

 is inexhaustible and opens up, when adequately used, a wide field 

 for quantitative investigation, not only with regard to the 

 quantitative description of subspecies, species, genera, etc., but 

 also for the study of the individual development. (See §§ 46 

 and 49-50.) 



Many specific characters are in reality measurable primordia. 

 Other characters may be brought into the form of measurable 

 primordia. Certain characters are compound properties which 

 may be decomposed into their primordial components. (See 

 § 38, segregation, p. 43.) 



A property, mentioned as a character, may, by analogy, lead 

 to the discovery of other similar properties which have never 

 been mentioned nor investigated before. 



It very often happens that a character, which exists in a large 

 number of species of a genus, a family, etc., is described in one 

 of them and not mentioned in all the others. In such cases it 

 is possible to investigate quantitatively the property under 

 consideration through a long series of species. By the applica- 

 tion of this method unexpected analogies and differences are 

 discovered and many interesting com-parisons are rendered 

 possible.^ This afEords an unhmited field for investigation. 



The principle of the primordia and the quantitative method 



1 A renowned embryologist of the modern school told me one day that it 

 was a waste of time to identify the animal species of which I was studying 

 the development ; he said also, expressing his contempt by a jest, that entomol- 

 ogy is the art oj counting hairs on the coccyx of beetles. By counting the joints 

 of the tarsus of innumerable species of Coleoptera, however, LATREILLE 

 found the base of classification of these insects. By counting the teeth and 

 the vertebrae, through the whole series of mammalia, most important results 

 have been attained (CUVIER, R. OWEN). Etc. 



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