222 



THE MONOTREMES. 



fidence for monotremes on one or other 

 hemisphere, if these actually represent a very 

 ancient group reduced at the present day to 

 a small number of descendants. But instead 

 of that we find the members of the group 

 restricted to a remarkably narrow area, an 

 area that could hardly be smaller the east 

 and south of Australia, Tasmania, and New 

 Guinea; and nowhere else has the slightest 

 trace of them been discovered either in the 

 fauna of the present day or in the deposits of 

 past geological epochs. Such a limited dis- 

 tribution belongs rather to types which have 

 had only a very brief past. 



In the present state of our knowledge we 

 can accordingly assert nothing positive con- 

 cerning the origin of this abnormal and highly 

 aberrant type. We can only say that the 

 facts, which must in any case be admitted to 



be very indeterminate, speak rather in favour 

 of a somewhat recent origination of this 

 group by degeneration from the marsupials. 

 But it is possible to defend all kinds of sur- 

 mises and hypotheses; and while some regard 

 the monotremes as direct descendants of the 

 fishes or reptiles, in favour of which view, it 

 must be admitted, the laying of eggs by 

 monotremes gives considerable weight; while 

 others again hold them to be degraded mar- 

 supials, which have degenerated through an 

 adaptation to a lower stage of development, 

 we must modestly confess that comparative 

 anatomy cannot decide in whose favour the 

 balance inclines. This science is, however, 

 so far, the only one that would have a word 

 to say on the subject, for neither the palaeon- 

 tology nor the embryology of these animals 

 is known. 



