1896.] "* [Bailey. 



his opinion, "the greater number of those variations which are usually 

 attributed to the direct influence of external conditions of life, are to be 

 attributed to panmixia. For example, the great variability of most 

 domesticated animals and plants essentially depends upon this principle." 

 In other words, certain differences are preserved through the agency of 

 natural selection, and certain differences are lost ; if the organism is 

 removed from this restraining and directing agency, all variations have 

 the chance of asserting themselves. "All individuals can reproduce 

 themselves," Weismann explains, " and thus stamp their characters upon 

 the species, and not only those which are in all respects, or in respect to 

 some single organ, the fittest." I am convinced that this term expresses 

 a very important truth, and one which, as Weismann says, is particularly 

 apparent in domestic animals and plants ; but panmixia does not express 

 an incident force. If new differences arise in consequence of the cessation 

 of the directive agency of natural selection, it is because they were first 

 impressed upon the organization by some unaccountable agency ; or, if 

 there is simply a falling away from accumulated characters, the residuary 

 or secondary features which appear are probably the compound and often 

 deteriorated result of various previous incident forces. In short, panmixia 

 is a name for a class of phenomena, and it cannot be considered as itself 

 an original cause of variation. It is, to my mind, largely the unrestrained 

 expression or unfolding of the growth-force consequent upon the removal 

 of the customary pressure under which the plant has lived. 



3. The Survival of the Unlike. 



The one note of the modern evolution speculations which has resounded 

 to the remotest corner of civilization, and which is the chief exponent of 

 current speculation respecting the origin and destiny of the organic 

 world, is Spencer's phrase, "the survival of the fittest." This epigram 

 is an epitome of Darwin's law of natural selection, or " the preservation, 

 during the battle for life, of varieties which possess any advantage in 

 structure, constitution or instinct." In most writings, these two phrases 

 — "natural selection" and "the survival of the fittest" — are used 

 synonymously ; but in their etymology they really stand to each other in 

 the relation of process and result. The operation of natural selection 

 results in the survival of the fittest. One must not be too exact, however,, 

 in the literal application of such summary expressions as these. Their 

 particular mission is to aftbrd a convenient and abbreviated formula for 

 the designation of important principles, for use in common writing and 

 speech, and not to express a literal truth. Darwin was himself well! 

 aware of the danger of the literal interpretation of the epigrahi " natural 

 selection." "The term 'natural selection,' " he writes, "is in some 

 respects a bad one, as it seems to imply conscious choice ; but this will be 

 disregarded after a little familiarity." This technical use of the term 

 " natural selection " is now generally accepted unconsciously; and yet 

 there have been recent revolts against it upon the score that it does not 



PROC. AMER. PHILOS. SOC. XXXV. 150. M. PRINTED JULY 9, 1896. 



