6 BRITISH JURASSIC GASTEROPODA. 



essence of a question which has been frequently asked of late years. Those who 

 ask such a question contend that, since the practical acceptance of the doctrine of 

 Evolution by the scientific world, the old binomial system is insufficient for the 

 requirements of biological knowledge. 



It will be remembered that an important congress of naturalists was held some 

 time ago at the British Museum under the presidency of Professor Flower, for the 

 purpose of discussing the subject of zoological nomenclature. All parties were 

 well represented — uncompromising binomialists, limited trinomialists, and thorough 

 trinomialists. As far as the philosophy of the subject in dispute went, it appeared 

 to me that the trinomialists had the best of it ; but when it came to a matter of 

 policy and practice, the more conservative side had much to say in favour of the 

 old method. In summing up, Professor Flower, who declared himself a limited 

 trinomialist, said that distinctly defined species undoubtedly exist in great numbers 

 owing to the extinction of intermediate forms; for such the binomial system 

 offers all that is needed in defining them. But infinite gradations are being traced, 

 both of present and especially of past forms ; in order to deal with these even a 

 trinomial system would in many cases be inadequate. He considered that sooner 

 or later far more radical changes would have to be introduced. 



These remarks refer more especially to the higher classes of creatures, but they 

 serve to show the danger of departing from the old course at present. It is not, 

 therefore, because I consider the binomial system the most philosophic or the 

 best, but because I consider it the least calculated to mislead under the circum- 

 stances that it has been adopted for this Monograph. We must jog on as well as 

 we can with the help of sub-genera and var. a and var. b, and this no doubt can 

 be done without any difficulty. Moreover, in the case of fossil mollusca, we must 

 never lose sight of the fact that, biologically, we are walking somewhat in the 

 dark, and also that mineralisation, by the changes it sometimes superinduces, adds 

 to our uncertainty in these matters. Hence the fossil-conchologist, treading on 

 somewhat doubtful ground, should not be over anxious to emphasise differences 

 the precise value and meaning of which are not so very obvious in all cases. 

 When we have to deal with a demoid group, such as some of the small Cerithia 

 for example, the larger the collection and the fewer the specific names we should 

 be disposed to give, whereas the varietal names would be numerous. It is, in fact, 

 these demoid forms with their numerous links which most require the assistance of 

 a third name. Of course these remarks have reference to the Jurassic Gastero- 

 poda only. The Cephalopoda might perhaps require somewhat different treat- 

 ment ; in fact, the difficulty as regards the Ammonites is practically got over by 

 splitting the genus, and even that method is hardly enough for such a sporting 

 group. 



