134 bulletin: museum of comparative zoology. 



eiii Gerinusel sei. Zur uiiterstiitznug der Ansiclit, class der Strang ein 

 Achsencylinder, d. h. ein Nervenzelleiifortsatz sei, fehlt der Nachweis 

 des thatsachlichen Zusammenhangs mit einer Nervenzellen.'' 



Viault ('76) and Rohon ('77) saw Reissner's fibre in plagiostomes 

 and agreed with Stieda that it was an artifact. 



Sanders ('78, p. 742), describing tlie central canal of the mullet, says : 

 " Occasionally a rod is seen in sections through this central canal of the 

 cord, which most probably is the coagulated liquid contained therein, as 

 Stieda suggested ; it is in only a few sections that this rod is seen, for 

 it usually falls out, not being retained in its place by any attachments." 



Mayser ('82, p. 295) found Reissner's fibre in the fourth ventricle in 

 tcleosts and followed it forward to the region of the trigeminal nerve. 

 He thought it might reach farther, and, contrary to the opinion of 

 Stieda and A'iault, agreed with its discoverer that it was probably 

 preformed. 



Sanders ('86, p. 740) failed to find the rod, or fibre, in plagiostomes, 

 but says : " There is often found a small quantity of granular matter in 

 the canalis centralis, which presents a granular appearance after co- 

 agulation ; it corresponds to the rod occasionally found in the canalis 

 centralis in the Teleostei, and shows perhaps that the cerebro-spinal 

 fluid coagulates more firmly in the latter than in the former." Some 

 years later Sanders ('94) found this structure of conspicuous size in 

 Myxine. 



Gadow ('91, p. 338) found Reissner's fibre in birds, but considered 

 it a product of shrunken cerebro-spinal fluid and lymph corpuscles. 

 If Reissner's fibre has been seen by other and later investigators, this 

 view has probably been accepted by them, as I find few further refer- 

 ences to this structure in later literature. 



In July, 1899, Studnicka published a short paper on Reissner's fibre 

 and its relation to the ventriculus terminalis. He mentions having 

 seen the fibre in many cyclostomes, selachians, teleosts, amphibians, and 

 amniotes, but the description is confined almost wholly to Petromyzon. 

 He denies that the fibre is an artifact formed from the cerebro-spinal 

 fluid, and believes it a preformed structure. He describes it as homo- 

 geneous, showing no evidence of internal structure. Some of his 

 observations are, however, opposed to this view. In Chimaera he some- 

 times found a parallel splitting of the fibre, and he describes it as 

 having in Anguilla an ' alveolar ' structure. In Petromyzon the fibre, 

 extending forward through the brain ventricles, may for a short dis- 

 tance penetrate the brain tissue, and again emerge into the ventricle. 



