CH. XLII. PALAEONTOLOGY. 477 



their relationship than when it was believed that those 

 creatures now known to us were all that had existed 

 since the creation of the world, while, at the same time, 

 they afford the evidence we need as to the lines of migra- 

 tion along which related living forms, now widely separated, 

 have passed to distant lands. Thus, if it were not that we 

 find marsupials in Europe in Triassic times, how could we 

 explain the presence of opossums in South America and 

 kangaroos in Australia, both of them marsupial forms, yet 

 existing at two ends of the world with no links between 

 them? So that, here again, as in plants, geographical distri- 

 bution has become a grand and interesting problem which 

 all naturalists may help to solve, and the theory of the 

 relationship and evolution of living forms brings order out 

 of confusion. We have only to turn to the grand volumes 

 on the different forms of animal life, brought home by the 

 * Challenger' expedition in 1876, to see how increasing 

 study and discovery lead to ever-widening generalisations, 

 uniting the whole of the living kingdom under a system of 

 natural and intelligible laws. Is it too much to say that, 

 with such a vista before him, and the certainty that any 

 observation he may conscientiously make will add to this 

 grand conclusion, the young student of Biology has a tempt- 

 ing field before him, and a reasonable prospect of doing 

 good work if he will only follow carefully in the footsteps of 

 such patient investigators as Linnaeus, Cuvier, and Darwin ? 



Concluding Bemarks. This short sketch gives but a 

 very imperfect glimpse of the kind of work which is being 

 done in science in our own days. The workers are now 

 hundreds, where in the seventeenth century they might 

 be reckoned by units, and the whole scope of their work 

 cannot yet be measured. We can therefore, in conclusion, 



