LEWIS. — POLYCHiETE ANNELIDS, 



231 



1. Giant nerve fibres ; truly nervous in 



nature. 

 '64, '64^ Leydig. 

 '78. Schultze. 

 '80. Langerlians. 

 '81. Spengel. 

 '83. Vignal. 

 '83. Jacoby. 

 '86. Leydig. 

 '87. Rohde. 

 '88. Friedlaender. 

 '89-91. Hatschek. 

 '89. Friedlaender. 

 '92. Cerfontaine. 

 '94. Friedlaender. 

 '95. Friedlaender. 



2. Canal nature ; axial canal or central 



canal. 

 '62. Claparede. 

 '62^ Claparede. 

 '62. Keferstein. 

 '63. Clarapede. 

 '64-'68. Ehlers. 

 '68. Claparede. 

 '69*. Claparede. 

 '73. Claparede. 



'74. GrefE. 

 '76. Semper. 

 '78. Vejdovsky. 

 '78. Mcintosh. 

 '79. Vejdovsky. 

 '80. Spengel. 



3. Homologous to chorda dorsahs of 



vertebrates. 

 '71. Kowalevsky. 

 '74. Semper. 

 '81. Perrier. 

 '85. Cunningham. 



4. Analogous to chorda, but not related 



genetically. 

 '82. Vejdovsky. 

 '83. Bulow. 



5. Degenerate nerve fibres; the sheath 



or tube-wall retained as an organ of 



support. 

 '87. Eisig. 

 '88-94. Lang (p. 221). 



6. Not nervous in nature because 



they do not respond to the Golgi 



method. 

 '92. Von Lenhosse'k. 

 '92-92^ Retzius. 



The latest work, and the most conclusive of all, upon the Leydig's 

 fibres, is that by Benedict Friedlaender. His observations and conclu- 

 sions are based upon a very broad and complete series of investigations, — 

 upon careful physiological experiments, as well as comparative morpho- 

 logical study. After investigating thoroughly both sheath and contents, 

 his conclusion is, that Leydig's fibres are true nerve fibres arising from 

 ganglionic cells, and further that they are mednllated nerve fibres of the 

 type found in vertebrates ; that the sheath agrees in structure, at least 

 in great part, with the myelin sheath of nerves in vertebrates, and that 

 the contents represent the axis cylinder. 



As his later papers are in full agreement with his earlier article of 

 1889, the words of the latter ('89, p. 258) may be quoted here : "Die 

 sogenannte Neurochorde von Mastobranchus, Lumbricus und sehr wahr- 

 scheinlich die der Anneliden iiberhaupt, . . . endlich die markhaltigen 

 Fasern der Wirbelthiere sind fundamental dieselben Gebilde." 



