Vol. XVIII. March, igro. No. 4. 



BIOLOGICAL BULLETIN 



THE SEAT OF SMELL IN THE CRAYFISH. 



S. J. HOLMES AND E. S. HOMUTH. 



The location of the sense of smell in the Crustacea has been 

 the subject of but few investigations. Putnam, Graber, Bateson, 

 Dearborn, Spaulding and others have made observations on the 

 reactions of various decapods to food at a distance from the body, 

 although they were not primarily concerned in tracing the seat 

 of the olfactory reactions. Herrick, working on the lobster, 

 found that most parts of the body were sensitive to ammonia and 

 clam juice. Experiments of Nagel ^ and Bethe ^ indicate that, in 

 the decapods, the first antennae have an important olfactory func- 

 tion, although both these investigators regard the olfactory sense 

 organs as not exclusively located in these appendages. Nagel 

 worked with Paguriis, Astacus and Carcinus. Removal of the 

 antennules of Pagiirus was followed by reactions to chemical 

 stimuli, although these were not so pronounced as before the 

 operation. Astacus in the presence of food was found to show 

 lively movements of the antennules, followed by movements of 

 the mouth parts and legs. Carcinus showed the same move- 

 ments of the mouth parts and antennae in the presence of food, 

 but it was only when food came into actual contact with the 

 mouth parts that efforts were made to secure it. Nagel's experi- 

 ments led him to conclude that sight and touch play a greater 

 part in locating food than the sense of smell. 



Bethe found that if a piece of meat is thrown into a dish with 

 several Carcinus there is no reaction at first. After several seconds 

 the antennules begin to wave rapidly and the maxillipeds move 

 slowly back and forth. The animals nearest the piece of meat 



I Bibliotheca Zoologica, Bd. i8, 1894. 

 "^ Archiv f.mik. Anat., Bd. 50, 1897. 



