Address of the President at the Annual Meeting. 
47 
If, then, it be asked how we are to distinguish the groups 
of Jixed from those of variable character, I answer, — in no 
other mode than by the comparison of large numbers of indi- 
viduals ; and by bringing together the subjects of our com- 
parison from the widest range of external conditions under 
which they are found to exist. It is only by a very extensive 
comparison of forms, even when brought from the same 
lo(iality, that we are justified in pronouncing a probable 
opinion as to their specific isolation ; so often does it happen 
that when we have chanced first to meet with two specimens 
which we should be disposed to rank as distinct species, on 
account of their obvious differences, the supposed boundary 
between them is altogether done away with by the subsequent 
discovery of osculant forms, which establish a complete transi- 
tion from one to the other, so that no line of demarcation can 
possibly be drawn between them. And when we come to com- 
pare together suites of specimens from different localities, the 
danger of error from reliance on a small number of individuals 
is still more multiplied ; since their divergent forms are likely 
to be more numerous and more strongly marked, and some of 
the intermediate links may be wanting. Even where such defi- 
ciencies exist, if we find two sets of forms manifestly tending 
one towards another, and each of them exhibiting a considera- 
ble range of variation, we shall generally, I feel sure, err on 
the right side in uniting them under a single specific designa- 
tion, rather than in ranking them as distinct species. 
The enormous multiplication of species which loads our 
systematic treatises and monographs, is in great measure due, 
I feel assured, to the neglect of this rule of comparing exten- 
sive series of individuals, and of taking particular note of the 
transitional forms. I could give you an example in which this 
has been done (within my own knowledge) to such an extent 
as, in the naming of shells from a new locality, to make three 
or four times as many species as can really be said to exist ; 
thus encumbering science with a vast number of useless de- 
scriptions, and placing those who may chance to come into 
possession of the intermediate forms, in the utmost perplexity 
as to the naming of their specimens in accordance (which they 
feel bound to do) with those descriptions. But I will adduce 
an illustration, drawn from a department of microscopic in- 
quiry, to which it is known to most of you that I have paid 
special attention, viz., the group of Forarninifera. Very 
early in my study of this group, which was commenced 
upon collections that were rather rich in individuals than in 
species, I came to the conclusion that it is (as a whole) pre- 
eminently distinguished by its capacity for variation ; and 
