Correlation and variation in internal and external characters in the common toad (Bufo lentiginosus americanus, Le C.)

The present study was undertaken with a view toward getting information first as to the degrees of correlation and variability of internal characters, such as the viscera and muscles, regarding which our knowledge is remarkably deficient, and second as to the general condition of correlation among a considerable number of characters in a single group of individuals.It has been pointed out frequently that selection acts not upon single characters or variations alone, nor as such, but upon the entire organism as the unit: that there results from this action a "balance of fitness"