1395.] Search for the Unknown Factors of Evolution. 427 
place we have little or no reason to believe that all the blasto- 
genic, gonagenic, or. gamogenic variations which may have 
arisen from various causes will become phylogenic. 
If we carry our analysis into the ‘plane of fitness’ the first 
point which arises is whether variations are normal, including 
both cenogenic and palingenic variations, or abnormal, includ- 
ing teratological and other malformations. The terms ‘ fortui- 
tous’ and ‘indefinite’ as opposed to ‘determinate’ and ‘ de- 
finite’ may be used apart from any theory, although they 
have sprung up as distinguishing two opposed views as to the 
principles of variation. ‘ Fortuity’ strictly implies variation 
round an average mean, while ‘definite’ is not the necessary 
equivalent of adaptive, but simply implies progressive or 
phylogenic variation in one direction which Waagen and 
Scott have termed “ Mutation.” Bateson’s terms ‘Continuous’ 
and ‘ Discontinuous’ are useful as distinguishing gradual from 
sudden ontogenic variation. 
In general our five working hypotheses as to the factors of 
evolution are theoretically related to the time stages of Varia- 
tion as seen in the following table :— 
a Gonagenic 
b Gamogenic 
Buffon’s 
c Embryogenic } St. Hilaire’s 
d Somatogenic , 
Darwin’s { i Phylogenic } KA N 
I again call attention to the fact that Neo-Darwinism has 
hitherto presupposed and practically assumed ‘fortuitous 
phylogenic variation’ as its basis, for it is solely related with 
the selection of those ontogenic variations which are also phylo- 
genic. Neo-Lamarckism, on the other hand, is solely con- 
nected with inheritable ‘somatogenic’ variation. Buffon’s 
factor of the ‘ direct action of the environment’ plays upon all 
four ontogenic stages, and both theoretically and as observed 
by experiment, produces profound ontogenic variations ; the 
question is, under what circumstances do such ontogenic varia- 
tion in each of the four stages become phylogenic? This 
