Febetjaey 28, 1896.] 



SGIENGE. 



303 



cite as an example the two genera, Hippo- 

 therium and Equus, of which the latter has 

 been asserted with good reason to have de- 

 scended from the former. It has been 

 shown, however, that the Equus eaballus 

 could not have descended from the Euro- 

 pean Hippotherium mediterraneimn, and hence 

 some writers have jumped to the conclusion 

 that the alleged phyletic relation of the two 

 genera does not exist. The reasons for de- 

 nying this descent are, however, presented 

 by specific chai-acters only, and the generic 

 characters are in no way affected. Further, 

 we know several species of Hippotherium 

 which could have given origin to the Equus 

 eaballus, probably through intermediate spe- 

 cies of Equus. 



Some naturalists are very uncritical in 

 criticising phylogenies in the manner I have 

 just described. They often neglect to as- 

 certain the definitions given by an author 

 to a group alleged by him to be ancestral; 

 but fitting to it some, definition of their 

 own, proceed to state that the ancestral 

 position assigned to it cannot be correct, 

 and to propose some new division to take 

 its place . It is necessary to examine, in such 

 cases, whether the new group so proposed is 

 not really included in the definition of the 

 old one which is discarded. 



The fact that existing genera, families, 

 etc., are contemporary need not invalidate 

 their phyletic relation. Gi'oup No. 1 must 

 havebeen contemporary with group ISTo. 2, at 

 the time that it gave origin to the latter, and 

 frequently, though always, a certain num- 

 ber of representatives of group JSTo. 1 have 

 not changed, but have persisted to later 

 periods. Some genera, as e. g., Crocodilus, 

 have given origin to other genera (i. e., 

 Diplocynodon) and have outlasted it, for 

 the latter genus is now extinct. The lung- 

 fishes, Ceratodus, are probably ancestral to 

 the Lepidosirens, but both exist to-day. 

 Series of genera, clearly phyletic, or Ba- 

 trachia Salientia, are contemporaries. Of 



course we expect that the paleontologic 

 record will show that their appearance in 

 time has been successive. But many an- 

 cestors are living at the same modern period 

 as their descendants, though not always in. 

 the same geographic region. 



III. NOMENOLATUEE. 



Nomenclature is like pens, ink and paper ; 

 it is not science, but it is essential to the 

 pursuit of science. It is, of course, for con- 

 venience that we use it, but it does not fol- 

 low from that that every kind of use of it is 

 convenient. It is a rather common form of 

 apology for misuse of it to state that as it is 

 a matter of convenience, it makes no differ- 

 ence how many or how few names we rec- 

 ognize or use. An illustration of this bad 

 method is the practice of subdividing a 

 genus of many species into many genera, 

 simpty because it has many species. The 

 author who does this ignores the fact that a 

 genus has a definite value, no matter 

 whether it has one or five hundred species. 

 I do not mean to maintain that the genus 

 or any other value has an absolute fixity in 

 all cases. They undoubtedly grade into 

 each other at particular places in the sys- 

 tem, 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 nomen- 

 clature 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 naturalists 

 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 con- 

 stitutes priority. Some of the aspects of 



