1865.] Sclater on the Mammals of Australia. 13 



bers would be well able to wield the pen, and might exercise con- 

 siderable influence upon Constituencies. For the present, then, we 

 reserve further comments, but when the proper time arrives, our aid 

 will not be found wanting, and if it be required, the little influence we 

 possess will be at the service of those whose interests these remarks 

 are intended to protect, and with whose labours in the cause of Science 

 we have the most sincere sympathy. 



THE MAMMALS OF AUSTEALIA. 



4 



By P. L. Sclater, M.A., Ph.D., F.E.S., Secretary to the Zoological 

 Society of London. 



The remains of extinct organisms have long since been adopted by 

 geologists as the only sure guide to the age of the strata in which 

 they are entombed. However dissimilar two formations may be in 

 other points, it is now universally acknowledged that, if they furnish 

 the same fossils, they must be considered as of the same period of 

 deposition. However much two formations may resemble each other 

 in composition, it is quite certain, if their fossils differ, that they 

 must be attributed to different geological epochs. Concerning the 

 origin of life upon this planet we can say nothing. But as to its 

 progress, we now know that from the remotest time to which we 

 have yet traced it back to the present moment, it has gone on in one 

 constantly-flowing but ever-varying stream, slowly yet surely chang- 

 ing its aspect as it moves forward, and never returning at any 

 subsequent period to the same appearance as that which it has before 

 presented. The further it advances, the greater is the amount of 

 variation. The present Flora and Fauna of the earth is more like 

 that of the tertiary period than that of the secondary, and the further 

 we go back into primeval time, the greater divergence we find in the 

 aspect of the animal and vegetable kingdoms. Thus it follows that the 

 amount of difference between the organic life of two successive epochs 

 becomes a measure of past time, and since the antiquated notion of an 

 indefinite number of separate creations has been discarded and the 

 great fact of the unity of organic nature acknowledged, it has been 

 generally recognized as such by all true philosophers. 



But it is not only the whole stream of life upon the globe that is 

 perpetually altering its general appearance ; each branch of it, as it 

 diverges from the parent stream, acquires an individuality of its own, 

 and becomes more different the longer it is separated from the main 

 channel. Upon re-entering this it again mixes with the general cur- 

 rent, and gradually loses the destructive features it has previously 

 acquired. This seems to have been the case with the Fauna of 

 Australia. Australia, judging from our present confessedly very im- 

 perfect knowledge of the history of its organic life, must have been 

 separated from the great mass of land which forms the Old World at 

 a time when Marsupialism was the prevalent, if not the only, form of 



