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SCIENCE, 



[N. S. Vol. IV. No. 85 



preservation we cannot learn mucli tliat we 

 wish to know of the structure of extinct 

 organisms. The nervous, vascular, mus- 

 cular and alimentary systems are entirely 

 lost and can be inferred only from indirect 

 and often insufficient evidence. Were the 

 pearly nautilus extinct, our notions of the 

 anatomy of the tetrabranchiate cephalopods 

 would be very much astray, and in the 

 cases of several groups of fossils we are 

 quite unable to interpret the structure from 

 what remains. 



(3) A third difficulty in the way of a 

 truly morphological paleontology consists 

 in the uncertainties of geological correla- 

 tion, by which the relative age of forma- 

 tions in widely separated areas and differ- 

 ent continents is to be determined. It may 

 and often does make a vital difference in 

 the construction of a phylogeny, whether a 

 given set of rocks in North America is 

 older or younger than one in Europe, with 

 which it is correlated. The principles ac- 

 cording to which such correlation is to be 

 made are still somewhat indeterminate, and 

 not a few geologists maintain that the prob- 

 lem is an insoluble one. On the other 

 hand, it is essential to the paleontologist 

 that it should be solved, and already a very 

 encouraging beginning has been made. 



(4) In the fourth place the apparent 

 order of succession of organisms in the strati- 

 fied rocks must not be too implicitly and 

 uncritically accepted. Animals and plants 

 diffuse themselves as widely as possible un- 

 til stopped by some impassable barrier. 

 During the long ages of the world's history 

 these migrations have ever been in progress, 

 and they greatly confuse the record when 

 we attempt to read it in terms of evolution- 

 ary descent. A species in a newer forma- 

 tion, which appears to be derived from one 

 in an older horizon of the same region, may, 

 as a matter of fact, have had an entirely 

 different ancestry and have migrated half 

 around the globe to the place where it oc- 



curs. To make these distinctions theoreti- 

 cally is easy; to apply them very difficult. 

 (5) Lastly should be mentioned a practi- 

 cal drawback to the paleontological method,, 

 namely, its costliness. The naturalist may 

 find much to do in other departments at 

 small expense, which will be a source of in- 

 finite pleasure to himself and of great value 

 to science. Every field and wood, every 

 pond and stream, and above all the sea,, 

 offer boundless stores of material. Even 

 the side of paleontology which bears upon 

 stratigraphy and historical geology may be 

 taken up to great advantage by the private 

 worker who happens to live in a favorable 

 locality. With paleontology as a branch of 

 morphology, however, the case is unhap- 

 pily very different. Here great collections 

 brought together without much regard ta 

 cost, skilled workers to prepare the speci- 

 mens, and great buildings in which to house 

 them are indispensable. Distant regions 

 must be examined and the whole world ran- 

 sacked for material. Many problems con- 

 nected with the ifforth American fauna must 

 await their explanation until Asia can be 

 thoroughly explored, while Africa and 

 South America have already shown what a 

 complete geological knowledge of those con- 

 tinents may be expected to teach. In this 

 country the arid parts of the West have 

 yielded a marvelous store of wonderfully 

 preserved fossils, but great sums have been 

 expended in gathering them — an oppor- 

 tunity which falls to the lot of but few. It 

 is to be hoped that the multiplication of 

 museums may ere long put within the reach 

 of all biological students something of these 

 great stores of wealth. 



It might well seem that all these limita- 

 tions and drawbacks would necessarily dis- 

 qualify paleontology as a morphological 

 subject from being of the smallest real im- 

 portance, but such a conclusion would be 

 highly erroneous. Several of the limita- 

 tions are but partial, not applying to par- 



