REACTIONS OF NECTURUS TO STIMULI THROUGH SKIN 101 



served to thrust their snouts above the water, open the mouth 

 wide, and then return to the bottom where they soon expel 

 the air, both through the gill-slits and from the mouth. It 

 would thus seem that, while the branchiae are the chief means 

 of respiration, the lungs play considerable part. 



The great tenacity of life showed by mud-puppies is a matter 

 of frequent comment. They are able to live for months with- 

 out food and may be easily revived after being left for three 

 or four hours out of water. After severe mutilation they re- 

 cover and regenerate lost parts. Notwithstanding this great 

 vitality they seem to fall easy victims to Saprolegnia, especially 

 if there is a slight abrasion on the skin. 



SUMMARY 



1. The skin of Necturus is everywhere sensitive to tactile 

 stimulation. The regions about the nostrils, gills and tail are 

 most sensitive and the back the least sensitive. 



2. Necturus is sensitive to chemical stimuli over the entire 

 body surface, the reactions being characteristic for the different 

 regions stimulated. The gills are usually the most sensitive 

 region, with the. nostrils and head following in order. 



3. Necturus is more sensitive to nitric than to hydrochloric 

 or sulphuric acid. It is least sensitive to acetic acid. It is 

 more sensitive to potassium sulphate than to potassium chloride. 



4. When any region of the body is fatigued for a given chem- 

 ical, it rarely responds to tactile stimuli, although it usually 

 reacts to other kinds of chemical stimuli. 



5. Necturus is sensitive to considerable changes in tempera- 

 ture. All parts of the body are sensitive to hot water (70° C), 

 but the gills, head and nostrils are the most sensitive regions. 



6. Necturus is negatively phototropic and comes to rest in 

 shaded areas. Both the eyes and skin are photoreceptors and 

 the stimulation of either brings about negative reactions. The 

 head and tail are the most sensitive regions. 



BIBLIOGRAPHY 



Copeland, M. The Olfactory Reactions of the Puffer or Swellfish, Speroides 



1912. maculatus (Block and Schneider). Jour. Exper. Zooi, 12, 363-368. 



1913. The Olfactory Reactions of the Spotted Newt, Diemyotylus viridescens 



(Rafinesque). Jour. Animal Behav., 3, 260-273. 

 Eyci.eshymer, A. C. The Habits of Necturus maculosus. Atner. Nat., 40, 123- 

 1906. 136. 



