BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 31, pp. 395-400 September 30, 1920 



VALUE AND USE OF STAGES IN DEVELOPMENT IN 

 TEACHING PALEONTOLOGY ^ 



BY ROBERT TRACY JACKSON 



{Read before the Society December SI, 1919) 



In the study of paleontology, one of two main objects ma}^ be the end 

 to be attained : First, where the fossils are studied as assemblages of 

 organic forms characteristic of certain beds and formations and from 

 them is gathered the key to unravel stratigraphy and build up the his- 

 torical record of the rocks. This important aspect of paleontology is 

 perhaps the leading line of paleontologic work at the present time, at 

 least among students of invertebrate fossils. Without decrying this work 

 in the slightest, it must be remembered that stratigraphy is an applica- 

 tion of paleontology and is not the whole subject. Its bearing is some- 

 what comparable to the study of geographical distribution to the student 

 of recent forms of animals and plants. 



The second object of paleontologic study is where fossils are studied 

 from the point of view of the structure, development, and systematic 

 affinities of the fossils themselves. This second method of study seeks to 

 give a definite knowledge of the organisms and of their morphologic and 

 systematic relations to other fossils in the faunas or floras of the past 

 and to the living organisms of the present day. Whatever the object to 

 be attained, it seems that at least in the beginning a student should 

 follow this second method in order to obtain an intelligent knowledge of 

 fossils. As Huxley wrote :'' 



"Already indications are not wanting tliat the vast multitude of fossil Arth- 

 ropods, Mollusks, Echinoderms and Zoophytes now known will yield satisfac- 

 tory evidence of the filiation of successive forms when the investigations of 

 paluiontologists are not merely actuated by the desire to discover time-marks 

 and to multiply species, but are guided by that perception of the importance 



^ Manuscript received by the Secretary of the Society February 10, 1920. 

 This paper is one of a series composing a symposium on the teaching of geology and 

 paleontology. 



2 Anatomy of Invertebrate Animals, London, 1877, page 6)87. 



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