‘SUCCESSION OF LIFE UPON THE GLOBE. 373 
the formation next above, than to that of any other series of 
deposits. Upon no other view can we comprehend why the 
Post-Tertiary Mammals of South America should consist prin- 
cipally of Edentates, Llamas, Tapirs, Peccaries, Platyrhine 
Monkeys, and other forms now characterising this continent ; 
whilst those of Australia should be wholly referable to the 
order of Marsupials. On no other view can we explain the 
common occurrence of “intermediate” or “ transitional ” 
forms of life, filling in the gaps between groups now widely 
distinct. 
On the other hand, there are facts which point clearly to the 
existence of some law other than that of evolution, and pro- 
bably of a deeper and more far-reaching character. Upon no 
theory of evolution can we find a satisfactory explanation for 
the constant introduction throughout geological time of new 
forms of life, which do not appear to have been preceded by 
pre-existent allied types. The Graptolites and Trilobites have 
no known predecessors, and leave no known successors. The 
Insects appear suddenly in the Devonian, and the Arachnides 
and Myriapods in the Carboniferous, under well-differentiated 
and highly-specialised types. The Dibranchiate Cephalopods 
appear with equal apparent suddenness in the older Mesozoic 
deposits, and no known type of the Paleozoic period can be 
pointed to as a possible ancestor. The A/ippuritide of the 
Cretaceous burst into a varied life to all appearance almost 
immediately after their first introduction into existence. The 
wonderful Dicotyledonous flora of the Upper Cretaceous 
period similarly surprises us without any prophetic annuncia- 
tion from the older Jurassic. 
Many other instances could be given; but enough has been 
said to show that there is a good deal to be said on both sides, 
and that the problem is one environed with profound difficul- 
ties. One point only seems now to be universally conceded, 
and that is, that the record of life in past time is not interrupted 
by gaps other than those due to the necessary imperfections of 
the fossiliferous series, to the fact that many animals are in- 
capable of preservation in a fossil condition, or to other causes 
of a like nature. All those who are entitled to speak on this 
head are agreed that the introduction of new and the destruc- 
tion of old species have been slow and gradual processes, in no 
sense of the term “‘catastrophistic.” Most are also willing to 
admit that ‘‘ Evolution” has taken place in the past, to a 
greater or less extent, and that a greater or less number of so- 
called species of fossil animals are really the modified descend- 
ants of pre-existent forms. ow this process of evolution has 
