1896. RULES OF NOMENCLATURE IN ZOOLOGY. 259 



other value has an absolute fixity in all cases. They undoubtedly 

 grade into each other at particular places in the system, but these 

 cases must be judged on their own merits. In general there is no 

 such gradation. 



" Nomenclature is then orderly because the things named have 

 definite relations which it is the business of taxonomy, and nomencla- 

 ture its spokesman, to state. Here we have a fixed basis of procedure. 

 In order to reach entire fixity, a rule which decides between rival 

 names for the same thing is in force. This is the natural and rational 

 law of priority. With the exception of some conservative botanists, 

 all naturahsts are, so far as I am aware, in the habit of observing this 

 rule. The result of a failure to do so is self-evident. There is, however, 

 some difference of opinion as to what constitutes priority. Some of 

 the aspects of the problem are simple, others more difficult. Thus 

 there is little or no difference of opinion as to the rule that the name 

 of a species is the first binomial which it received. This is not a 

 single date for all species, since some early authors who used trinomials 

 and polynomials occasionally used binomials. A second rule which is 

 found in all the codes, is that a name in order to be a candidate for 

 adoption, must be accompanied by a descriptive diagnosis or a plate. 

 As divisions above species cannot be defined by a plate, a description 

 is essential in every such case. 



" It is on the question of description that a certain amount of 

 difference of opinion exists. From the codes of the Association for 

 the Advancement of Science, and of the Zoological Congresses, no 

 difference of opinion can be inferred, but the practice of a number of 

 naturalists both zoologists and palaeontologists in America, and 

 palaeontologists in Europe, is not in accord with the rule requiring 

 definition of all groups above species. It has always appeared to me 

 remarkable that a rule of such self-evident necessity should not meet 

 with universal adoption. However, the objections to it, such as they 

 are, I will briefly consider. It is alleged that the definitions when 

 first given are more or less imperfect, and have to be subsequently 

 amended, hence it is argued they have no authority. However, the 

 first definitions, if drawn up with reference to the principles 

 enumerated in the first part of this address, need not be imperfect. 

 Also an old-time diagnosis of a division which we have subsequently 

 found it necessary to divide, is not imperfect on that account alone, 

 but it may be, and often is, the definition of a higher group. But you 

 are familiar with all this class of objections and the answers to them, 

 so I will refer only to the positive reasons which have induced the 

 majority of naturalists to adhere to the rule. 



" It is self-evident that so soon as we abandon definitions for 

 words, we have left science and have gone into a kind of literature. 

 In pursuing such a course we load ourselves with rubbish, and place 

 ourselves in a position to have more of it placed upon us. The load 

 of necessary names is quite sufficient, and we must have a reason for 

 every one of them, in order to feel that it is necessary to carry it. 

 Next, it is essential that every line of scientific writing should be 

 intelligible. A man should be required to give a sufficient reason for 

 everything that he does in science. Thus much on behalf of clear- 

 ness and precision. There is another aspect of the case which is 

 ethical. I am aware that some students do not think that ethical 

 considerations should enter into scientific work. To this I answer 

 that I do not know of any field of human labour into which ethical 

 considerations do not necessarily enter. The reasons for sustaining 

 the law of priority are partly ethical, forwe instinctively wish to see 



