32 GENERAL 1>REL!MINAET CONSIDERATIONS. 



of animals will long be the chief book of reference for all who 

 take an interest in the subject. I would refer the reader to 

 Wallace's book, and think I may therefore fairly refrain from 

 adducing numerous instances to prove that in the present 

 distribution of animals on the globe an equally sharp demar- 

 cation of the stratification of the groups of animals can be dis- 

 cerned as of the topography of the organs in an individual 

 organism. No one will expect to find living Marsupials in 

 England or Germany, or buffaloes, stags, and other Ruminants 

 in Australia. The reader who is acquainted with Wallace's 

 work on the contrast between the faunas of the Australian 

 and In do-Malayan provinces will not have been surprised — on 

 the contrary will have felt a certain satisfaction — at hearing 

 that an animal has lately been discovered in New Guinea be- 

 longing to the group of the Monotremata and nearly allied to 

 the Ornithorhynohus. 



If we could describe the embryology of these groups of faura 

 — i.e. if we were in a position to represent the development of 

 each distinct fauna, from the earliest geological periods down 

 to our own time with anything approaching to the same com- 

 pleteness as we can now attain with regard to the embryology 

 of many animals — we should undoubtedly be able to trace the 

 present distribution of animals up to very remote geological 

 periods. The brilliant results, far transcending all that had 

 been previously achieved, of the palseontological investigations 

 in North America by the American naturalists, who annually 

 risk their lives to obtain scientific results, will undoubtedly 

 ere long put them in a position to give us an almost complete 

 history of the secular evolution of the North American fauna ; 

 and I am convinced that tho elucidation of this branch of 

 natural history will not only reveal many more important inter- 

 mediate forms between diflFerent vertebrate types than are now 

 known, but also that tho main features of the present distri- 

 bution of the North American Yertebrata will be recognisable 

 in that of the fossil fauna, precisely as the general arrangement 

 of the organs, in which the most dissimilar animals agree, is 

 indicated from the first in the primary germinal layers. 



Enough has been said, I hope, to prove that we are justified 



