ORGANIC EVOLUTION 355 
It is believed that in still older rocks a five-toed form will be 
discovered, which was the parent of the four-toed form. 
In the collections at Yale College there are preserved 
upward of thirty steps or stages in the history of the horse 
family, showing that it arose by evolution or gradual change 
from a four- or five-toed ancestor of about the size of a fox, 
and that it passed through many changes, besides increase 
in size, in the two million years in which we can get facts 
as to its history. 
Remarkable as is this feature of the Marsh collection at 
New Haven, it is now surpassed by that in the Museum of 
Natural History in New York City. Here, through the 
munificent gifts of the late W. C. Whitney, there has been 
accumulated the most complete and extensive collection of 
fossil horses in the world. This embraced, in 1904, some 
portions of 710 fossil horses, 146 having been derived from 
explorations under the Whitnev fund. The extraordinary 
character of the collection is shown from the fact that it 
contains five complete skeletons of fossil horses—more than 
existed at that time in all other museums of the world. 
The specimens in this remarkable collection show phases in 
the parallel development of three or four distinct races of horse- 
like animals, and this opens a fine problem in comparative 
anatomy; viz., to separate those in the direct line of ancestry 
of our modern horse from all the others. This has been 
accomplished by Osborn, and through his critical analysis 
we have become aware of the fact that the races of fossil 
horses had not been distinguished in any earlier studies. 
As a result of these studies, a new ancestry of the horse, 
differing in details from that given by Huxley and Marsh, is 
forthcoming. 
Fig. 105 shows the bones of the foreleg of the modern 
horse, and Fig. 106 some of the modifications through which 
it has passed. Fig. 107 shows a reconstruction of the ances- 
