CHAIN OF CYCLOSALPA AFFINIS 441 
Ueber die gréssere oder geringere Haufigkeit des Sichtbarwerdens 
semilatenter Eigenschaften entscheidet nicht nur die augenblickliche 
Lebenslage, d.h. die dusseren Einfliisse wahrend der empfindlichen 
Periode der Entwickelung. Fast ebenso gross ist die Bedeutung der 
individuellen Kraft des Jungen Pflanzentheiles, diese aber ist das Ergeb- 
niss der Wirkung der dusseren Factoren in den vorhergehenden Zeit- 
abschnitten, theils nach Wochen und Monaten, theils nach Jahren 
gerechnet. . . . Diese Erscheinung tritt am deutlichsten zu Tage 
in der Periodicitéit der Anomalien auf der Pflanze. 
Again, pushing the matter a step farther, and in a somewhat 
different direction: 
From a broad point of view, fluctuating variability falls under two 
heads. They obey quite the same laws and are therefore easily con- 
fused, but with respect to questions of heredity they should be carefully 
separated. They are designated by the terms individual, and partial 
fluctuation. Individual variability indicates the differences between 
individuals, while partial variability is limited to the deviations shown by 
the parts of one organism from the average stature.” (’05, p. 717). 
The individual differences seem to be due, at least in a very 
great measure, to such apparent trifles. (As differences in soil, moisture, 
light, etc.). Onthe other hand partial differences are often manifestly 
due to similar causes. . . . The development of the leaves is depend- 
ent on their position, whether inserted on strong or weak branches, ex- 
posed to more or less light, or nourished by strong or weak roots (p. 721). 
Then follows the quotation already given, viz., ““This dependency upon 
local nutrition, ete.” 
De Vries’ standpoint seems clear: Periodicity in plants is a 
special form of the more general phenomenon of fluctuating varia- 
tion which in turn is due to ‘dusseren Factoren.’ The quanti- 
tative differences that manifest themselves in the periods may 
be lumped together and treated according to the law of probabil- 
ity as first applied to organic beings by Quetelet. After illustra- 
ting the application of the method of statistics, the author says: 
“Tt should be repeated once more that the empirical result is 
3 It would be very interesting to have deVries follow up this point critically and 
impartially. 
