IN RELATION TO ZOOLOGICAL DISTINCTION. 57 



The diameters of the erythrocytes of different species have been made 

 the subject of study especially by Gulliver, Wormley, Schmidt, Welcker, 

 Malassez, Formad, and Treadwell. Gulliver's investigations extended over 

 a period of 35 years and included studies of about 650 species. He frankly 

 states that his tables can not pretend to absolute exactness, and are only 

 offered for what they may be worth, and that in the estimation of their 

 value allowance should be made for errors, whether instrumental or personal, 

 more or less inevitable, notwithstanding the greatest care, in observations 

 so extensive, and that the relative value of the measurements, though 

 probably not unexceptionable, may be entitled to more confidence as fair 

 approximation to the truth. He further states that in spite of little mis- 

 takes or of variations in the dimensions of the corpuscles of this or that 

 species, the comparative results will appear sufficiently uniform. Gulliver's 

 measurements are so closely in accord with those of later observers that 

 they are to be accepted as being sufficiently accurate to serve for purposes 

 of comparison. His investigations were made from the point of view of the 

 biologist, and he claims that the differences in the measurements of the 

 erythrocytes of different species constitute an important means of zoo- 

 logical distinction. Thus, he states: 



If we compare the red corpuscles of species of one order or family, e. g., Tragulus 

 and other ruminants, the corpuscles of the former animals will constantly prove the 

 smallest; so, too, in Paradoxurus and Cam's, in Hippopotamus and Elephas, in Mus 

 and HydrochoeTus, in Dasypus villosus and Orycteropus capensis, in Rhea americana and 

 Casuarius, in Zootica vivipara and Anguis fragilis, in Bujo viridis and Bufo vulgaris, 

 in Osmerus eperlanus and Salmo salar. And in like manner the facts are equally clear 

 in comparison of the different orders, so that the corpuscles are smaller in the Rumi- 

 nantia than in the Rodentia, in the Marsupialia than in the Edentata, in the Graminivora 

 than in Rapaces, in Anura than in Urodela, in Sturiones than in Plagiostomi. 



Notwithstanding the foregoing positive statement, there seems to be 

 a general, if not universal, belief that the size of the corpuscles is without 

 much zoological importance, which is indicated by the very infrequent, 

 casual, and scanty references to this subject. There is no doubt that the 

 figures show unequivocally that the mean diameters of the erythrocytes 

 of different genera, related or unrelated, may be practically the same, as, 

 for instance, those of the monkey, lipped bear, hyena, and rhinoceros; 

 and again, those of man, opossum, dingo, dog, wolf, whale, armadillo, 

 beaver, capybara, guinea-pig, muskrat, etc. Nevertheless, it is clear that 

 even among the members of a given order, or tribe, or genus, etc., the 

 differences may be sufficient to be positively distinctive, and at times to 

 have some other and more special zoological significance. Thus, in the 

 primates there is seemingly an increase in the size of the corpuscles as the 

 individual is higher in the scale of life, as, for instance, man, 7.9^; chim- 

 panzee, 7.4 [i ; monkey, 7.1^; lemur, 6.4 p. This relationship may be in rela- 

 tion to differences in the sizes of the species (page 58) . Another interesting 

 relationship is noted in the horse, mule, and ass, the mule being a hybrid 

 and the corpuscles having an intermediate measurement. Then again, 

 comparing representatives of classes of different orders, such as ruminants, 

 felines, canines, etc., not only may each class be readily distinguished 



