406 Mr. F. O. P. Cambridge—A Revision 
elimination tempered by definite selection or citation—the 
one object held in view being the narrowing, as early as 
possible in the history of a genus, the area within which the 
type species must be sought for, always presuming that this 
shall be one of those species originally included when the 
genus was first founded and the generic name bestowed. 
The Problem before us. 
We must, then, in connexion with this problem make up 
our minds on the following points :— 
A. Asto the date from which our nomenclature is to begin. 
B. As to the necessity for fixing upon a single species as 
the type of each genus. 
C. As to the method of fixing upon a single species as the 
type in the case of heterotypical genera. 
With regard to the first point: in my paper referred to 
above I had not excluded the names published by Clerck in 
1757, because I considered that they answered all the require- 
ments of the binomial system. It is of course quite absurd 
to exclude Clerck merely because he wrote one year earlier 
than the date arbitrarily fixed upon as the point whence our 
nomenclature should start—the tenth edition of Linneus, 
1758. 
None the less, however, I agree with Dahl that if we are 
to accept the tenth edition as the starting-point, then Clerck’s 
names must go; for this is just a case in point where we 
shall never get agreement unless we adhere absolutely to this 
first rule. ‘There is no question of right or wrong in the 
matter, nor even of common sense—rather the contrary ; it is 
simply a question of convenience, a step taken for “ purely 
practical purposes,’ as Dr. Dahl himself suggests, in order to 
avoid disputation and to bring arachnological nomenclature 
into line with that of other branches of zoology. 
B.—It is not necessary to enlarge upon the necessity of 
fixing upon a single species as the type. This, again, is a 
purely practical question, for theoretically there is no type of 
a genus. And this practical type is a species, in the case of 
arachnology consisting of two sexes, round which others 
group themselves, their characters fining away all round the 
circumference, where they pass into other adjacent groups. 
Practically we have to decide upon the species which is to be 
regarded as the centre of this group. 
Dr. Dahl, in pointing out that the International Rules make 
no mention of the right of an author to select a type, adds 
that ‘ they speak only of the original type, and tn this they do 
