Volume XVII. June, I go I. No. 2. 



JOURNAL 



MORPHOLOGY. 



NOTES ON AEOLOSOMA TENEBRARUM. 



EDITH M. BRACE. 



Aeolosoma tenebraruniy a fresh-water oligochaete belonging 

 to the Aphaneura, has been supposed to hold a unique posi- 

 tion among annelids, having been described as having a brain 

 but no ventral nerve cord, 



Vejdovsky, Maggi, and Beddard have given the more de- 

 tailed accounts of its structure. Vejdovsky^ found a few cells 

 supposed to represent a rudimentary nerve cord which was not 

 connected with the bilobed brain : " Bei A. tenebranim treten 

 auf der Bauchseite zerstreute Elemente hervor, die auf eine 

 nervose Natur hinweisen." And again : "Man erkennt in der 

 Centrallinie der Bauchseite, eine kurze Strecke hinter der 

 Pharyngealregion, eigenthiimliche, aber sehr undeutliche Zellen- 

 und Fasserstrange, die jedoch mit dem Gehirnganglion nicht 

 zusammenhangen." From the plates it is impossible to tell 

 just what cells are referred to, but as they were found in the 

 median line, they could not have been a part of the ventral cord. 



Maggi 2 has described a brain, ventral cord, and lateral nerves 

 for Aeolosoma : " Un cordone schiacciato che si estende lungo 



1 Vejdovsky, F. System und Morphologie der Oligochaeta. 1884. 



2 Maggi, L. Intorno al genera Aeolosoma. 1865. 



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