EXPERIMENTS ON MOLLUSKS 133 



the remaining functions of the arms, for instance, loco- 

 motion and steering. 



The fact discovered by v. Uexkiill that the basal 

 ganglion, when no longer connected with the central 

 nervous system, produces coordinated chewing move- 

 ments when stimulated is of great importance for the 

 segmental theory. The skin and muscles are in this 

 case connected by nerve-fibres which do not pass 

 through the central nervous system but through a 

 peripheral ganglion that v. Uexkull terms the bucco- 

 intestinal ganglion. This is another fact that speaks 

 for the idea that the ganglia are only to be considered 

 as organs of transmission, that is, as connecting pro- 

 toplasmic threads for reflexes, and not as bearers of 

 mysterious reflex mechanisms. 



BIBLIOGRAPHY. 



1. STEINER, J. Die Functionen des Centralnervensy stems der 

 wirbellosen Thiere. Sitzungsberichte der Berliner Academic der 

 Wisscnschaften, 1890, i., p. 32. 



2. V. UEXKULL. Physiologische Untersuchungen an Eledone 

 moschata. Zeitsch. f. Biologic, Bd. xxxi., 1895. 



3. STEINER, J. Die Functionen des Centralnervensystems und 

 ihre Phylogenese. III. Abtheilung. Die wirbellosen Thiere, Braun- 

 schweig, 1898. 



