Febbuaky 28, 1896.] 



SCIENCE. 



?01 



cannot be said to exist. In illustration I 

 cite the case of the eruption of a tooth. Be- 

 fore it passes the line of the alveolus it is 

 not in use ; it is not in place as an adult or- 

 ganism. When it passes that line it has be- 

 come mature, has reached its expression 

 point, comes into functional use, and may be 

 counted as a character. Such will be found 

 to be the case with all separate parts; there 

 always will be a time when they are not 

 completed and then there will be a time 

 when they are. These lines, then, will al- 

 ways remain as our boundaries, as they are 

 now, for all natural divisions from the 

 generic upwards. This condition cannot ex- 

 ist in characters of proportionate dimen- 

 sions, which will necessarily exhibit com- 

 plete transitions in evolution. Hence, pro- 

 portions alone can only be used ultimately 

 as speciiic characters. 



Some systematists desire to regard phy- 

 letic series as the only natural divisions. 

 This may be the ultimate outcome of pa- 

 leontologic discovery, but at present such a 

 practice seems to me to be premature. In 

 the first place, as all natural divisions 

 rest on characters, we must continue to 

 depend on their indications, no matter 

 whether the result gives us phyletic series 

 or not. In the next place, we must remem- 

 ber that we have in every country interrup- 

 tions in the sequence of the geological for- 

 mations,which will give us structural breaks 

 until they are filled. There are also periods 

 when organic remains were not preserved ; 

 these also will give us interruptions in our 

 series. So v/e shall have to adhere to our 

 customary method without regard to theoiy, 

 and if the phyletic idea is correct, as I be- 

 lieve it to be, it will appear in the final re- 

 sult, and at some future time. 



Authors are frequently careless in their 

 definitions. Very often they include, in 

 the definition of the order, characters which 

 belong in that of the family, and in that of 

 the family those that belong in the genus. 



Characters of diiferent values are thus 

 mixed. The tendency, especially with nat- 

 uralists who have only studied limited 

 groups, is to overestimate the importance 

 of characters. Thus the tendency is to 

 propose too many genera and other divi- 

 sions of the higher grades. In some groups 

 structure has been lost sight of altogether, 

 and color patterns, dimensions, and even 

 geographical range, treated as characters of 

 genera. As the mass of knowledge in- 

 creases, however, the necessity for precision 

 will become so pressing that this kind of 

 foi'mulation will be discarded, and defini- 

 tions which mean something will be em- 

 ployed. Search will be made especially 

 for that one character which the nature of 

 the series renders it probable will survive, 

 as discoveries of intermediate forms are 

 successively made, and here the tact and 

 precision of the taxonomist has the oppor- 

 tunity for exercise. In the selection of 

 these characters, one problem will occasion- 

 allj^ present itself. The sexes of the same 

 species sometimes disjday great disparity 

 of developmental status, sometimes the 

 male, but more frequently the female, re- 

 maining in a relatively immature stage, or 

 in others presenting an extraordinary de- 

 generacy. In these cases the sex that dis- 

 plays what one might call the genius, or in 

 other words, the tendency, of the entire 

 group, wiU furnish the definitions. This 

 will generally be that one which displays 

 the most numerous characters. In both 

 the cases mentioned the male will furnish 

 these rather than the female; but in a few 

 cases the female furnishes them. The fact 

 that both sexes do not present them does 

 not invalidate them, any more than the 

 possession of distinct reproductive systems 

 would refer the sexes to different natural 

 divisions. 



I have seen characters objected to as of 

 little value because they were absent or 

 inconstant in the young. I only mention 



