SECTION 22 OBSERVATION. 309 



seven years, we should be ready to find that some cells are 

 replaced at frequent intervals, whilst others, such as the neural 

 cells, never, or altogether, pass away; or instead of assuming 

 that all twins intimately resemble each other, we might discover 

 that there are two types those closely resembling each other, 

 developed from the same egg, and those plainly different, 

 produced from two different eggs; or we might learn that 

 "there are upland geese with webbed feet, ground woodpeckers, 

 diving thrushes, and petrels with the habits of auks" (Darwin); 

 or we might discover that a certain lowland plant transferred 

 to a high plateau assumes the features of a certain highland 

 plant and loses these when returned to the valley, but that 

 the highland plant translated to the valley retains its highland 

 characteristics; or experience might enlighten us about whis- 

 pering galleries and opaque acoustic "clouds", and not only 

 teach us that cooling water begins to expand at 4 C., but that 

 in certain circumstances it may be cooled down to over ten 

 degrees below C. without freezing ; or experiment might 

 teach us that living larvaB might be produced by chemical 

 changes from unfertilised eggs in the case of diverse species- 

 starfish, sea-urchins, holothurians, and others; or alertness 

 might enable us to connect avian polyneuritis with human beri- 

 beri, and also to assume that there may be life-endangering 

 deficiency diseases which can be cured by the simple process 

 of supplying what is lacking; or we might find, contrary to 

 anticipation, that at the beginning of the week's work and the 

 first hour of work in the morning less is produced than after 

 the first day and after the first" hour, and that during the last 

 hour before lunch and before leaving work in the evening 

 more is produced relatively to some of the intervening hours, 

 and that those working fewer hours produce, within large 

 limits, correspondingly more. Seeming incongruities should be 

 fastened on as possible new centres of departure instead of as 

 matters to be ignored or explained away, as with the anomalous 

 position of argon and iodine in the Periodical Table of the 

 elements. 1 Darwin, according to his son, was above all things 

 a believer in alertness: "There was one quality of mind which 

 seemed to be of special and extreme advantage in leading him to 



1 "If some opposite instance, not observed or not known before, chance to 

 come in the way, the axiom is rescued and preserved by some frivolous dis- 

 tinction; whereas the truer course would be to correct the axiom itself." 

 (Bacon, Novum Organum, bk. 1, 25.) Some famous instances of this kind should 

 not. be overlooked. When it was shown that water did not rise higher in 

 a pump than thirty-two feet, it was contended that nature's horror of a 

 vacuum ceased at that limit; when it was demonstrated that the supposed 

 loss of substance in combustion could be accounted for, it was argued that 

 phlogiston possessed the characteristic of positive levity ; and when Darwin 

 proposed his theory of natural selection, attempts were made to modify the 

 theories of special creation so that they might be in formal consonance 

 with the results of geological and biological research. 



