267 



matter. Sports, therefore, of which the ancon sheep was certainly one, may be 

 phylogenetic. Scott, however, has recently shown, Am. J. Science, 369, 1894, that 

 many if not most saltatory variations are of an entirely different nature from the 

 variations that in the past have given rise to phylogenetic series. In a deviation 

 much less marked, such for instance as the presence of one more than the normal 

 number of spines in a fin, this ultimate criterion of transmission might fail us 

 even were it practicable to put it to the test. A surer way of determining 

 phylogenetic variation is to measure variation in the bulk by means of curves. 

 If, say one thou.sand individuals of a definite time and place, show in the aggre- 

 gate a character different from that normal to the species, it is phylogenetic. Such 

 variations may occur in successive years or at isolated places. The phylogenetic 

 character is in such a case really made up of a large number of ontogenetic vari- 

 ations which must also be capable of reappearing; that is, they must also be 

 phylogenetic. A better way of stating the problem would seem to me to be that: 

 All variations are ontogenetic, some are at the same time immediately phylo- 

 genetic and many if not all may become so— a phyletic series. This leaves open 

 the question of the conditions under wbicli ontogenetic variation becomes phylo- 

 genetic and ignores the unchanged germ[)lasm theory which from jjurely embryo- 

 logical grounds is untenable. 



The paragraphs pertaining to this subject in the following direction are: 7. 

 8, 13, 15, 16. 



Nearly synonymous terms with ontogenetic and phylogenetic are the terms 

 variation and mutation as used by Newmayr, Waagen, and Scott. Variation is 

 here applied to locally different forms, while mutation is applied to the chronolog- 

 ical changes or "steady advance (of the mean) along certain definite lines." The 

 latter term may for our purpose be still further restricted by applying it not only 

 to the changes of the mean in successive geologic periods, but to the changes in the 

 mean which may occur in two successive years or broods. 



To quote Newmayr, pp. 60-61 (from Scott, p. 372), " Weil ein Theil der Merk- 

 male gleichmiissig nacli einer Richtung im Laufe der Zeit mutirt, zeigen andere 

 Oharactere regellose Abiinderungen und jede Mutation entwickelt denselben 

 Varietiitenkreis." Scott illustrates this process by comparing the mutation to the 

 progress of a cyclone center and the continual circlet of variations to the circu- 

 lating winds. 



