JANUARY 17 



life is shown by the remains of Diprodoton australis, a 

 gigantic extinct marsupial of the bulk of a hippopotamus. 



Why, then, did these pouches go out of fashion ? Why 

 did the placental type of mammal supersede the mar- 

 supial in all parts of the globe except Australia ? And 

 why, if the marsupial form failed in other lands, has it 

 proved so enduring in Australia alone ? No answer comes 

 from the past to questions such as these, nothing but 

 feeble speculation, or, at most, suggestion drawn from 

 analogy with other instances of extinction. Speculation 

 based upon such shadowy grounds regarding problems in 

 biology is seldom worth attention ; yet, seeing that there 

 is no penalty upon its indulgence, I shall venture to offer 

 an irresponsible essay in that line. 



About fifteen years ago there was discovered in Australia 

 a kind of mole (Notary ctes typhlops) hitherto unknown to 

 science. The mode of this creature's life seems to have 

 had a destructive effect upon one of its most important 

 organs that of sight. In our own mole (Talpa europcea) 

 the skeleton has been modified so as to adapt it perfectly 

 to its peculiar habits. The eyes also are minute, and 

 closely environed with fur, so as to offer a minimum of 

 sensitive surface to grains of earth or sand ; but they 

 exhibit no signs of deterioration, except in size. For 

 practical purposes they remain effective organs of vision. 

 In the Australian mole it is different ; the eyes are far 

 gone in degeneration further, affirms Miss G. Sweet, who 

 has made a special study of this rare creature, than in 

 any other burrowing mammal, ' the retina being generally 

 reduced to a mass of simple cells, and the cornea and 

 sclerotic (white of the eye) to a pear-shaped capsule 

 enclosing a ball of pigment.' In short, the dry sandy soil 



