52 BIOLOGICAL LECTURES. 



buildings in which to house them are indispensable. Distant 

 regions must be examined and the whole world ransacked for 

 material. Many problems connected with the North Ameri- 

 can 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 

 continents 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 opportunity 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 marvelous stores of wealth. 



It might well seem that all these limitations and drawbacks 

 would necessarily disqualify palaeontology as a morphological 

 subject from being of the smallest real importance, but such a 

 conclusion would be highly erroneous. Several of the limita- 

 tions are but partial, not applying to particular cases, while 

 others are difficulties that further investigation may hope to 

 remove, not insurmountable obstacles. Every year new forms 

 are discovered and better material of known forms. Though 



o 



the White River Bad Lands have for more than half a century 

 been classic collecting ground, hardly a season passes that 

 several new genera are not registered from there, and, better 

 still, types before known only from fragments are gradually 

 made more and more complete. From the middle Eocene to 

 the lower Miocene there is in the West an almost unbroken 

 transition which is bringing forth a truly magnificent series of 

 evolutionary stages. 



While palaeontology, as we have seen, does not profess to 

 give an unbroken life-history of the earth, yet it has certain 

 preeminent advantages which neither comparative anatomy nor 

 embryology possesses, and which fit it to form an invaluable 

 supplement to those other methods of morphological investiga- 

 tion. 



(i) In the first place, it gives us in many cases actual 

 phyletic series in their true order of succession in time. In 

 many groups of animals we have already recovered phyletic 



