8 



have not living representatives ; and often the fossil species found 

 in this deposit are identical vnt\i those still existing. Another very 

 interesting and instructive fact is also exhibited — many of the 

 forms of animals which are now perfectly differentiated into 

 distinct families or even orders, were, in the earlier deposits, not 

 so differentiated. On the contrary, remains are constantly found 

 in which the characters of totally distinct families are blended — 

 in other words, a generalised type then existed wliich, in more 

 recent deposits, and in living species, has given way to more 

 specialised types. 



In a few cases the pedigree of a species has been well made 

 out, the fossil links in the chain of evolution being almost perfect. 

 The development of the horse, a one-toed animal, from a four-toed 

 ancestor, is a case in point. 



Zoogeography. — With regard to the distribution of life on the 

 earth, there are two branches of the subject. 1st, the distribution 

 of animals on land (aerial), and in water (aquatic) ; and 2nd, their 

 distribution over different areas of the earth's surface. On the 

 theory of separate creation, we ought to find that among the 

 aerial animals, differentiated as they are into groups adapted for 

 that mode of life, aquatic animals would not be found, and on the 

 other hand, those groups eminently adapted for aquatic existence 

 would be expected to confine themselves to the water ; but we do 

 not find such to be the case. For instance, the SAvans, geese, and 

 ducks are all web-footed and clearly adapted for an aquatic life. 

 Now the swans leave the water but rarely, and progress on land 

 with difficulty; the geese spend much of their time out of the 

 water, and in Australia we find the ceriopsis goose, which very 

 rarely, if ever, seeks the water, and is as much a land bird as a 

 partridge. It is, however, clearly a goose, autl has webbed-feet. 

 Among the ducks there is the tree-duck, wliich habitually frequents 

 trees, and several species breed in holes of trees, like woodpeckers. 

 Still more startling is the mode of life adapted by certain species 

 of thrushes, a thoroughly aerial and generally arboreal group, yet the 

 dippers — genuine thrushes — dive exceedingly well, holding on to the 

 stones at the bottom of rapid streams, using tlieir wings to swim 

 with, and feeding almost entirely on aquatic insects, small .shell-fish, 



