458 



W. J. CROZIER 



of heterogeneous constitution. This conclusion may be extended 

 to include the surface of chemoreceptors, since it enables us to 

 account not only for the reactions of the earthworm to dilutions 

 of acids (Crozier, '16), but also clears up a well known anomaly 

 in regard to human taste. 



It was shown by Richards ('98) and by Kahlenberg ('98) that 

 the hydrogen ion muSt in some way be responsible for the sour 

 taste. Yet acetic acid, which ceases to be tasted at dilutions 



eo 



70 



So 



g -90 



tS 30 



so 



.0 



(?>-J 



5 10 90 95 100 



Per cent ionization 



Fig. 2 The relation between percentage ionization and time of cell pene- 

 tration from solutions of hydrochloric, butyric, and acetic acids. 



1, Acetic acid 



3, Butyric acid \ integument of Chromodoris zebra. 

 5, Hydrochloric acid 



2, Butyric acid 



4, Hydrochloric acid 

 /, 3, 5, from Crozier ('16). 

 2. A. from Harvey ('14c). 



testis epithelium of Stichopus ananus. 



