Record. lvii 



tives on glass, and spoke briefly on the relation between 

 negative and positive in photographic plates, showing that 

 there is a certain relation between intensity of actinic light 

 acting on the plate during exposure and during development, 

 as a result of which a greatly overexposed plate may be de- 

 veloped into a positive instead of a negative, by allowing 

 access of a limited quantity of light during development, 

 while a plate which has been very briefly exposed may in the 

 same manner be developed into a positive by a proportionate 

 increase in the light allowed to fall on it during develop- 

 ment, — a neutral or zero point, in which the plate is com- 

 pletely fogged, being passed in each instance. 



Mr. G. Pauls exhibited a number of beautiful caterpillars, 

 the larvae of Evphydryas phaeton, which does not appear to 

 have been hitherto recorded as occurring in Missouri, although 

 Scudder reports it from adjoining States. The food plant on 

 which these were found was a species of Gerardia. 



Dr. H. von Schrenk exhibited a burl on the branch of 

 Mississippi scrub pine, caused by a rust fungus, Peridermium 

 cerebrum, which was in excellent fruit. 



Mr. Pierre Chouteau, Mrs. Pierre Chouteau and Dr. W. B. 

 Outten, of St. Louis, and Professor John H. Frick, of War- 

 renton, Missouri, were elected to active membership. 



Two persons were proposed for active membership. 



May 21, 1900. 



President Engler in the chair, twenty-four persons present. 



A paper by Dr. Adolph Alt, entitled Original contributions 

 concerning the glandular structures appertaining to the human 

 eye and its appendages, was presented by title and referred 

 to the Council. 



Dr. M. A. Goldstein read a paper on the physiology of 

 voice production, in which he discussed three essential factors 

 in the production of voice, the motor force, the organ of 

 sound, and the resonators. The essential features presented 

 may be summarized as follows : ( 1 ) All elements carefully 

 considered, the best form of breathing applicable to voice 

 production and singing is the rational combination of the 



