66 



Scientific Proceedings (27). 



month a sharp decrease in plasticity occurs as is indicated by the 

 rise of the index from 106 to 146. 



3. The racial indices of modifiability, obtained by averaging 

 the results for five individuals of each sex for each of the three ages 

 mentioned, indicate a rapid decrease in plasticity from 94 at one 

 month to 169 at seven months of age. 



Discussion of these results is not in order in the present unfin- 

 ished state of the investigation. I may say, however, that I am 

 attempting to ascertain the duration of the sexual life of the dancer, 

 and to discover the relation of plasticity to the strength of the 

 electric stimulus which the animal learns to avoid. 



37 (293) 



The crystallography of hemoglobins. 

 By EDWARD T. REICHERT and AMOS P. BROWN. 



[From the S. Weir Mitchell Laboratory of Physiology, University of 



Pennsylvania.^ 



The primary object of this research was to determine whether 

 or not corresponding albuminous substances are identical. We 

 believed that if non-identity were established we should have a 

 fact of great fundamental importance in relation to heredity, the 

 origin of species, etc. The crystallographic method was adopted 

 because we believed that by this means we might succeed where 

 the chemist has failed ; and hemoglobin was selected as the first 

 substance of our inquiry because of its comparatively ready crys- 

 tallizability. Crystals from over one hundred species have been 

 studied, and we have not only positively shown the non-identity 

 of the hemoglobins, but have also brought to light much informa- 

 tion of broad biological interest. From a preliminary review of 

 our records certain facts stand out very prominently. 



1 . The constancy of generic characters in the crystals. — For 

 instance, the genera that have been represented by a considerable 

 number of species, as Felis, Canis, Papio, etc., show in each case con- 

 stancy in the characters of the crystals in each genus, with marked 

 differences both in axial ratios and in crystal systems between the 



