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LIFE-FORMS OF THE PAST AND PRESENT. 
BY HENRY WOODWARD, F.G.S., F.Z.S., 
Op the British Museum. 
[PLATES XC. and XCI.] 
O NE of the most interesting results at which the naturalist 
arrives in extending his researches from the living pre- 
sent far back into the remote periods of geological time, is 
that he finds existing between the life-forms of the past and 
present, not merely accidental likenesses or analogies, hut 
actual homologies and relationships. There is, in fact, no 
ground whatever for the old, and to. some extent, still prevalent 
dogma, that the several faunas and floras, which in past ages 
successively peopled and clothed the surface of the earth, had 
no direct relationship, either with each other, or with existing 
types. 
Indeed, so strong was this feeling in the minds of nearly all 
the earlier observers, that they hesitated to compare extinct 
organisms with living forms, and were content to accept the 
dictum of those geologists who taught that each series of 
fossiliferous deposits was a distinct creation, being separated by 
a universal cataclysm alike from the preceding and subsequent 
life-periods. It is less than twenty years since the modern 
doctrine of continuity of life on the earth began to be received 
and adopted as the basis of all sound palaeontological reasoning ; 
and notwithstanding the numerous breaks that still exist, it is 
nevertheless possible, by reviewing the life-history of any 
particular class or order, to demonstrate that a real continuity 
does exist from the earliest representative down to the forms of 
to-day. 
I propose to take, by way of illustration, a few examples from 
a class which offers perhaps the widest geographical and geo- 
logical range, combined with the greatest diversity of detail in 
organisation, of any among the Invertebrate kingdom, namely 
the Crustacea ; confining myself mainly to two of the most 
ancient orders, the Merostomata and the Trilobita. 
In tracing a group like the Crustacea further and yet 
