Note W — Chapter V · EXPLANATION OF THE OBSERVATIONS

All told, there are hardly more than half dozen experimental investigations of the color-sense in mammals,—to speak only of these. Three of them deserve especial mention. One, the work of the American, Kinnaman,[33] on two Rhesus monkeys. Then a brief but careful piece of work by Himstedt and Nagel.[34] These two investigators were able to determine that their trained poodle could distinguish red of any tone or shade from the other colors, and from Professor Nagel I learned that later the tests were extended and the same was shown to be true concerning the blue and the green. And finally there is an investigation which hitherto has been known only from a reference which Professor Dahl,[35] the investigator, himself makes. The work is on a monkey, Cercopithecus (Chlorocebus) griseoviridis Desm. (Professor Dahl has kindly allowed me to look over the records of the experiments. He intends to publish the monograph at an early date.)

All of these investigators arrive at the conclusion that the animals tested by them possess color-sense. The monkey last-mentioned shows one peculiarity: it was unable to distinguish a saturated blue from the black. It will require further tests to clear this up.