156 A. J. CARLSON. 



negative ; neither nerve cells nor nerves could be found. The 

 uniform negative results were generally taken to indicate that 

 nervous elements are not present in the heart of this interesting 

 group of animals. But Hunter (1902) has recently found nerves 

 and nerve cells in the heart of Molgula manhattensis. The 

 nerve cells, mostly of the bipolar type, are most abundant at 

 either end of the heart, situated on the surface of the muscular 

 walls under the pericardium. The same observer has later 

 (1903) found evidence to the effect that the cluster of nerve 

 cells or ganglia at either end of the heart are connected by 

 nerve fibres with the central nervous system. 



BIBLIOGRAPHY. 

 Alder, J., and Hancock, A 



1845 Monograph of British Nudibranchiate Mollusca. London. 



de Quatrefages, M. A. 



1849 Memoire sur le Genere Taret (Terredo Lin.). Ann. Sc. Nat. Zool., 3 

 ser., XL, p. 19. 



Hancock, A., and Embleton, D. 



1852 On the Anatomy of Doris. Philosophical Transactions, Part I., p. 207. 

 Lacaze-Duthiers . 



1857 Historic Anatomique et Physiologic du Pleurobranche Orange. Ann. Sc. 

 Nat. Zool., 3 ser., p. 275. 



Lacaze-Duthiers. 



1859 Memoire sur le Systeme Nerveux de 1'Haliotide. Ann. Sc. Nat. Zoo!., 4 

 ser., XII. 



Cheron, J. 



1866 Recherches pour servir a 1'Histoire du Systeme Nerveux des Cephalopodes 



Dibranchiaux. Ann. Sc. Nat. Zool., V. , p. 5. 

 Bert, P. 



1867 Memoire sur la Physiologic de la Seiche. Mem. Soc. Sc. de Bordeaux, V. 

 Lemoine. 



1868 Recherches pour servir a 1'Histoire des Systeme Nerveux Musculaire et 



Glandulaire de 1'Ecrevisse. Ann. Sc. Nat. Zool., IX.' 

 Berger, E. 



1876 Ueber das Vorkommen von Ganglienzellen im Herzen des Flusskrebses. 



Sitzungsber. d. k. Akad. z. Wien, LXXIV. , Abt. I. 

 Darwin, F. 



1876 On the structure of the snail's heart. Journal of Anatomy and Physiology, 

 X.,p. 506. 



Dogiel, J. 



1877 Die Muskeln and Nerven bei einigen Mollusken. Archiv fur mikroskop- 

 ische Anatomic, XIV., p. 59. 



