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THE AMEBIC AX NATURALIST [Vol. XLIV 



a mutant. Let $ represent again such a chance occurrence. Then 

 (f> is a function of a, b, c, certain difficultly understood conditions 

 which seem to reside within particular gametes and produce a 

 new variety, differing considerably from the parental forms. 

 The various occurrence of mutants among domestic animals 

 probably resulted from such internal conditions. The very light 

 silver cat, Chinnie, made his appearance about 1878, and has 

 been the stock ancestor from which all the line-bred silver cats 

 have since been produced. No external factors determining the 

 occurrence of this sport could be traced. DeVries, who, of 

 course, emphasizes these chance occurrences of the mutants, 

 seems to believe that the internal conditions are alone respon- 

 sible for these chance variations, yet MacDougal is said to have 

 produced mutants of the evening primrose by salt solutions. If 

 this observation is borne out by subsequent investigation, such 

 mutant-producing factors would be represented by m. n, o of our 

 formula, the external conditions for the production of chance oc- 

 currence <t>, in this case the mutant. 



3. Lastly, the concept of chance is of frequent occurrence in 

 Mendelian literature. The Mendelian formula for the produc- 

 tion of generation F u demands that the independent inheritable 

 characters shall separate in the gametes of F l and recombine 

 according to the pure law of chance, and .Mendel's work on peas 

 bears this out to a remarkable degree of accuracy. Similarly if 

 we believe that the sex of certain arthropods is determined by 

 male and female producing spermatozoa, but the egg is neutral, 

 we must assume that the determination of sex is purely a matter 

 of the chance union of the male or the female producing sperma- 

 tozoa with a neutral egg. Nor in this case is the formula of <f> 

 without its significance. The work on certain parthenogenetic 

 forms shows that certain spermatozoa, those without the acces- 

 sory chromosome, are degenerate and presumably non-func- 

 tional. This degeneration is obviously an internal condition, a, 

 of the formula, but since it is known that various sex ratios ex- 

 ist all the way from the approximate one to one of many of the 

 mammals to the very disproportionate ratios, approaching par- 

 thenogenesis in the nematodes, it may be supposed that this in- 

 ternal degeneration of certain of the spermatozoa is itself the 



