THE OPOSSUM 



61 



other beasts. Nevertheless, it is now certain that it truly 

 lays eggs, and that the same is the case with* the 



echidna. 



FIG. 17. 



THE ORNITHORHYNCHUS. 



But these two animals differ from all other beasts in 

 so many and such important points that they almost 

 form a sort of zoological half-way house between birds 



