128 VARIATION AND DIFFERENTIATION IN CERATOPHYLLUM. 



in a single case of a very general and fundamental biological law. This 

 law has been differently stated, according to the particular class of 

 phenomena in which it is seen to be operating. Thus Jennings ( :05) , 

 dealing with the facts of behavior, calls it the ''law of the readier reso- 

 lution of physiological states" and formulates it in the way which has 

 already been quoted (p. 108). He gives a number of examples showing 

 the evidence in favor of the law from the behavior of lower organisms 

 and says (p. 485) : ' 'In view of the facts, it is probable that the law is 

 a general one and that it will be demonstrated in some form for other 

 lower organisms." He also suggests the probability that the essential 

 principle embodied in the law will be found to operate in morphogenetic 

 processes. Definite statistical proof that such is in fact the case has 

 been given by the present paper. Possibly a word of explanation is 

 necessary to bring out the fact that the essential principle in the law 

 as stated by Jennings is the same as that which underlies our law of 

 diminishing variability. This will be clear if we consider in a little 

 more detail the facts of behavior which led to the formulation of the law 

 from that point of view. By analyzing certain phenomena of behavior 

 in detail, Jennings {loc. cit, p. 481) shows that: 



In the lowest organisms we find individual adjustment or regulation on the basis 

 of the three following facts : 



(1) Definite internal processes are occurring in organisms. 



(2) Interference with these processes causes a change of behavior and varied 

 movements, subjecting the organism to many different conditions. 



(3) One of these conditions relieves the interference with the internal processes, 

 so that the changes in behavior cease, and the relieving condition is thus retained. 

 * * * 



Now an additional factor enters the problem. By the process which we have just 

 considered, the organism reaches in time a movement that brings relief from the 

 interfering conditions. This relieving process becomes fixed through the operation of 

 a certain law which appears to hold throughout organic activities. This law may 

 be stated as follows: An action performed or a physiological state reached is 

 performed or reached more rapidly after one or more repetitions, so that in time it 

 becomes "habitual." 



While, as Jennings points out, this statement of the law is not entirely 

 adequate, yet it emphasizes the point at which comparison between the 

 facts of behavior and morphogenesis may most easily be made. If in 

 the production of successive whorls on an axis of a Ceratophyllum plant 

 the variation about the type for each whorl diminishes, while, as has 

 been shown, the type of the whorls changes at an ever-decreasing rate, 

 it merely means that the production of a particular type of whorl tends, 

 speaking in purely descriptive terms, to become "habitual." In both 

 the psychological and morphogenetic cases there is a tendency to produce 



