772 REPORT—1896. 
Attention has just been directed to the probable importance of former 
climatic changes in determining the distribution of organisms, but the whole 
subject of the geographical distribution of organisms during former geological 
periods, though it has already received a considerable amount of attention, will 
doubtless have much further light thrown upon it as the result of careful observations 
carried out amongst the stratified rocks. 
So long ago as 1855, Pictet laid it down as a paleontological law that ‘the 
geographical distribution of species found in the strata was more extended than 
the range of species of existing faunas.’ One would naturally expect that at a 
time when the diversity of animal organisation was not so great as it now is, 
the species, having fewer enemies with which to cope, and on the whole not too 
complex organisations to be affected by outward circumstances, would spread 
further laterally than they now do; but as we know that in earliest Cambrian 
times the diversity of organisation was very considerable, it is doubtful whether 
any appreciable difference would be exerted upon lateral distribution then and 
now, owing to this cause. At the time at which Pictet wrote, the rich fauna of 
the deeper parts of the oceans, with its many widely distributed forms of life, 
was unknown, and the range in space of early organisms must have then struck 
every one who thought upon the subject as being greater than that of the shallow- 
water organisms of existing seas, which were alone known. It is by no means: 
clear, however, with our present knowledce, that Pictet’s supposed law holds 
good, and it will require a considerable amount of work before it can be 
shown to be even apparently true. Our lists of the fossils of different 
areas are not sufficiently complete to allow us to generalise with safety, but 
a comparison of the faunas of Australia and Britain indicates a larger 
percentage of forms common to the two areas, as we examine higher groups of 
the geological column. If this indication be fully borne out by further work, it 
will not prove the actual truth of the law, for the apparent wider distribution of 
ancient forms of life might be due to the greater probability of elevation of 
ancient deep-sea sediments than of more modern ones which have not been sub- 
jected to so many elevatory movements. Still, if the law be apparently true, it is 
a matter of some importance to geologists; and I have touched upon the matter 
here in order once again to emphasise the possibility of correlating comparatively 
small thicknesses of strata in distant regions by their included organisms. 
Mention of Pictet’s laws, one of which states that fossil animals were con- 
structed upon the same plan as existing ones, leads me to remark upon the 
frequent assumption that certain fossils are closely related to living groups, when 
the resemblances between the hard parts of the living and extinct forms are only 
of the most general character. There is a natural tendency to compare a fossil 
with its nearest living ally, but the comparison has probably been often pushed 
too far, with the result that biologists have frequently been led to look for the 
ancestors of one living group exclusively amongst forms of life which are closely 
related to those of another living group. The result of detailed work is to bring 
out more and more prominently the very important differences between some 
ancient forms and any living creature, and to throw doubts on certain compari- 
sons; thus I find several of the well-known fossils of the Old Red Sandstone, 
formerly referred without hesitation to the fishes, are now doubtfully placed in 
that class. 
The importance of detailed observation in the field is becoming every day more 
apparent, and the specialist who remains in his museum examining the collections 
amassed by the labours of others, and never notes the mode of occurrence of 
fossils in the strata, will perhaps soon be extinct, himself an illustration of the 
principle of the survival of the fittest. In the first place such a worker can 
never grasp the true significance of the changes wrought on fossil relics after they 
have become entombed in the strata, especially amongst those rocks which have 
been subjected to profound earth-movements; and it is to be feared that many 
.‘ species’ are still retained in our fossil lists, whose supposed sperific characters 
are due to distortion by pressure. But a point of greater importance is, that one 
who confines his attention to museums cannot, unless the information supplied to 
