62 DWIGHT E. MINNICH 



response. Internal stimuli due to prolonged inanition, or exter- 

 nal chemical stimuli of an adventitious sort, too dilute for my 

 detection, may perhaps explain these responses, though a certain 

 statement concerning them is not possible. 



Without multiplying examples, the above are sufficient to 

 illustrate the behavior in question. One of the chief purposes 

 of the preliminary trial was to detect responses of this sort and 

 thus avoid an occasional misinterpretation. If there was but one 

 barely visible jerk of the proboscis coil as the animal was pulled 

 off the wall of the cage, and no further sign of extension during 

 the preliminary trial, experimentation was continued. If, how- 

 ever, there was any more significant movement of the proboscis 

 during the preliminary procedure, experimentation was discon- 

 tinued and not resumed for at least fifteen minutes. Usually there 

 was no evidence of response in the second prehminary, but in 

 case there was, experimentation was again discontinued for a 

 minimum period of fifteen minutes. 



The maximum duration of all trials, preliminary and final, 

 unless otherwise stated, was one minute. Failure to observe any 

 visible movement of the proboscis during this period constituted 

 a 'no response.' If the proboscis was partially extended early 

 in a trial, the trial was continued, to ascertain whether complete 

 extension would result. If the proboscis was completely ex- 

 tended, the trial was immediately terminated, and the animal 

 returned to its cage. Trials thus lasted one minute or less, 

 depending upon the response. 



The chemical stimuh employed consisted of distilled water, and 

 three aqueous solutions, viz., IM saccharose, 2M NaCl, and 

 M/10 quinine hydrochloride. The saccharose and quinine hydro- 

 chloride were USP quality; the sodium chloride, CP quality. 

 The solutes being non-volatile, the distance stimulus afforded by 

 each of the solutions was identical with that afforded by distilled 

 water, viz., water vapor. In other words, the four stimuli used 

 could be distinguished, if distinguished at all, only through 

 direct contact. 



With the exception of quinine hydrochloride, the stimuli 

 selected were substances frequently encountered by Pyrameis in 



