88 BIOLOGICAL LECTURES. 



both cenogenic and palingenic variations, or abnormal, including 

 teratological and other malformations. The terms ' fortuitous ' 

 and 'indefinite' as opposed to 'determinate' and 'definite' 

 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 aver- 

 age 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 " Muta- 

 tion." 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 : — 



Ontogenic 



a Gonagenic 



b Gamogenic 



Buffon's<j Allei 



c Embryogenic}St. Hilaire's 



d Somatogenic ) ^ 

 T~, -If „, , . > Lamarck s 

 Darwm's{ |^ Phylogenic \ 



I again call attention to the fact that Neo-Darwinism has 

 hitherto presupposed and practically assumed ' fortuitous phylo- 

 genic 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 vari- 

 ations in each of the four stages become phylogenic.^ This 

 factor would be partly but not wholly set aside by proof that 

 somatogenic variations are not inherited. St. Hilaire's factor 

 of the action of environment upon early stages of development 

 would result in purely fortuitous variations, and, as he himself 

 clearly perceived, would require Selection to give it an adaptive 



