466 Transactions of the Society. 
of study, and make it all the better a field for investigation of 
“ species ”? 
It must not be thought that I in the least advocate the dis- 
regard of intermediate forms as such ; on the contrary, I believe they 
should receive more careful attention than has hitherto generally been 
given to them. The indiscriminate multiplication of species which I 
deprecate is in most cases due to the attention of systematists 
having been too much concentrated on what they have considered 
to be “ typical ” specimens ; while those which might be referred to 
either of two types have been neglected and passed over. Equal 
attention ought to be paid to such intermediates, in order to ascertain 
whether they are sufficiently numerous and close to completely con- 
nect the types between which they stand. Such work is more likely 
to lead to good results, and to increase our knowledge, than the estab- 
lishment of any number of “ new species ” on hasty and insufficient 
observation. 
If Nature is found not to support the ideas of systematists as to 
what a “ species ” should be, systematists will eventually have to con- 
form to the teaching of Nature as to what a “ species ” is ; or will, 
at any rate, be guided to a decision as to whether “ species ” exist in 
Nature at all. 
To scientifically determine this latter point, it is requisite to 
observe and record with care, not merely casually but systematically, 
all intermediate forms, with the special view of ascertaining whether 
living diatoms do indeed form the “continuous chain” of Dr. Van 
Heurck, or whether there now exist definite gaps, dividing them 
into what, I submit, should then be regarded as “ natural ” species. 
Should this be found to be the case, we can next inquire whether 
fossil forms, partially or entirely, bridge over these gaps ; and if so, 
at what horizon of time and space. Such an investigation will throw 
light not only on the fact of evolution, but possibly also on its history. 
The ultimate result may indeed be a revolution, perhaps in the 
direction indicated by Prof. Huxley, compelling us to relinquish 
altogether the idea of species as “ definite entities ” ; but perhaps 
only, I venture to think, in the direction of greatly extending our 
idea of their comprehensiveness. 
So far as my own acquaintance with diatoms has gone, I believe 
they tend to support the latter view ; but I freely confess that my 
own knowledge, and I think also the investigations of other dia- 
tomists, are not sufficient to justify a confident opinion. All I 
venture to contend, therefore, is, that the question should still be 
regarded as an open one. 
