314 C. F. MABSHALL. 



Mr. Cunningham for much advice and help in conducting the experi- 

 ments, nearly all the more important of which were witnessed by him. 



As this paper does not profess to be a complete account of the 

 physiology of the nervous system of the lobster, I shall not attempt 

 to give an exhaustive account of the literature of the subject, but only 

 refer to such papers as bear directly on the questions stated above. 

 The most important paper dealing with these questions is one by 

 Emile Yung, entitled " Physiologie de la chaine gangiionaire chez les 

 crustaces." x This paper I was unfortunately unable to obtain access 

 to till after my experiments had been completed. Although many of 

 my results were anticipated by Yung, yet, since my methods of in- 

 vestigation differ for the most part from those employed by him, I 

 think it worth while publishing them. Confirmatory results arrived 

 at independently are always of value in experimental physiology. 



Two other papers, one by Richet, " Contribution a la physiologie 

 des centres nerveux et des muscles de l'ecrevisse," 2 and another by 

 Fredericq et Vandevelde, " Physiologie des muscles et des nerfs du 

 homard," 3 deal only with the phenomena of muscle and nerve and the 

 various conditions of muscular excitability, and do not bear on the 

 subject of this paper. Mr. J. Ward has written a short paper " Some 

 Notes on the Physiology of the Nervous System of Astacus Fluvia- 

 tilis." i His results were obtained by cutting the nerves and replacing 

 the animals in running water and observing the subsequent movements. 

 Mr. Ward came to the conclusion that there was no evidence of decus- 

 sation of nerves in the central nervous system of the Crayfish. The 

 most recent contribution is a short note by Eeichenbach, " Beobach- 

 tungen tiber die Physiologie des Nervensystems vom Flusskrebs." 5 

 This I was unfortunately unable to obtain. 



I shall now give a detailed account of my investigations dealing 

 first with the anatomy and then with the physiology, and compare my 

 results with those obtained by Yung. 



A. Anatomy. 

 1. Thoracic Nerves. — Arising from each of the thoracic ganglia, with 

 the exception of the supra- and sub-oesophageal ganglia, there are two 



1 Archives de Zoologie, t. VII, 1878. 



a Archives de Physiologie normale et pathologique, t. VI, 1879. 



3 Bulletin de VAcaddmie royale de Belgique, 2 e s6rie, t. 47, 1879, 



* Journal of Physiology, vol. II., 1879-80. 



6 In Humboldt, Bd. I., p. 26-27, 1883. 



