Chromosomes and Genes 187 



the same extent but may overlap. These changes may be repatterning 

 by rearrangement breaks within or near the overlapping sections; they 

 may be repatterning by loss of parts (deficiency) of a section of 

 diflFerent size; they may be submicroscopic rearrangements like in- 

 versions and, even more probably, submicroscopic deletions. The latter 

 might be called absences in the sense of Bateson and also Stadler; but 

 it is not the absence which counts, but the disturbance of a definite 

 pattern, a position efiFect in our description of this phenomenon. The 

 deficiency, microscopic or submicroscopic, does not act by an absence 

 of something but as one of the different ways in which a definite 

 pattern, necessary for normal function, can be changed. It is thus not 

 different in action and causation from any other rearrangement. Any- 

 body who wishes to see these things clearly should look closely at the 

 fact, now proved in a number of instances reported before, that 

 homozygous deficiencies for a locus or "gene" produce the same effect 

 as the mutant locus, and, also, of any other position effect of a break 

 nearby. Since the facts cannot be doubted any longer, and since it is 

 a logical procedure to explain them by a single concept embracing 

 the entire field of manifestations and structure of the genie material, I 

 cannot see how we can make progress without adopting ideas based 

 upon patterns and their changes as underlying the behavior of the 

 genie material. 



I must criticize severely the statements, found in the literature, 

 which maintain that only a few geneticists follow me (which is be- 

 coming less true every day), though at the same time it is acknowl- 

 edged that the theory of the gene is in a state of crisis. If a way out 

 of the "crisis" has been shown, why not try it instead of glancing 

 backward longingly at the good old gene? I think that this attitude is 

 just as bad as the formerly quoted pronunciamento that geneticists 

 who have different ideas from the classic ones do not know what they 

 are talking about. 



At this point mention should be made of a recent very fine dis- 

 cussion of the opposing points of view by Stadler (1954), in a post- 

 humous paper. He believes that the difference can be solved by 

 introducing Bridgman's idea of operational procedure as opposed to 

 hypothetical. (See also Chovnick and Fox, 1953.) This means that a 

 phenomenon cannot be defined in terms of assumed properties beyond 

 experimental determination, but must be defined in terms of the actual 

 operations applied. Thus, operationally, a gene cannot be defined 

 otherwise than as the smallest segment of the "gene string" that is 

 associated with a typical effect. The difference between what I repre- 



