SPENCER, Lord, on selection in breeding.
SPENCER, HERBERT, on the "survival of the fittest." -increase of fertility by domestication. -on life. -changes produced by external conditions. -effects of use on organs. -ascent of the sap in trees. -correlation exemplified in the Irish elk. -on "physiological units." -antagonism of growth and reproduction.
SPERMATOPHORES of the cephalopoda.
SPERMATOZOIDS.
SPHINGIDAE, sterility of, in captivity.
SPINOLA, on the injurious effect produced by flowering buckwheat on white pigs.
SPITZ dog.
SPOONER, W.C., cross-breeding of sheep. -on the effects of crossing. -on crossing cattle. -individual sterility.
SPORES, reproduction of abnormal forms by.
SPORTS. -in pigeons.