Chemical Taxonomy

Abstract

THE differences between species of animals and of plants are ultimately chemical, and Ford¹ has shown in butterflies that classification based upon morphology corresponds with chemical differences in pigments. The distinction between two species within a genus must be due, in part at least, to differences between their proteins. Such differences cannot be shown by ordinary chemical methods, but in the case of one protein, namely, hæmoglobin, differences have lately been found by spectroscopic means between several species of the crustacean genus Daphnia². In this genus it has long been a matter of discussion as to whether the species D. obtusa Kurz is really worthy of specific rank or is merely a variety of D. pulex (De Geer). Scourfield has, however, recently discovered a new, clear-cut morphological distinction between the two forms which confirms the specific rank of D. obtusa³. In these circumstances it is particularly interesting to find that their haemoglobins also differ². Another such instance of spectroscopic evidence in a case of doubtful specificity can now be reported.