STRUCTURE AND DEVELOPMENT OF REISSNEr’s FIBRE’. 15 
the startling mistahes in the earlier of the two papers h}' 
Sargent, with whose work he appears so entirely in agreement. 
Ill 1901, Cole and Johnstone (’01) drew attention to the 
occurrence of Reissner’s fibre in the canalis centralis of 
Pleuronectes, and appear to have accepted Sargent’s 
theory without question. 
Dendy, early in 1902, unaware that it had been previously 
described or figured, directed attention to the sub-commissiii’al 
organ, which he spoke of as a “[lair of ciliated grooves.” 
He noted the occurrence, in the amraocoetes of Petromyzon 
and Geotria, of a pair of conspicuous grooves lined by long- 
columnar epithelium, the free boi-der of which was beset with 
short cilia. These grooves were described as beginning at 
the posterior limit of the habenular ganglia, and e.xtending 
backwards beneath the posterior commissure to the hinder 
end of that structure. He suggested that these grooves 
were concerned in promoting the circulation of the cerebro- 
spinal fluid. 
Kblliker (’02) announced that he had observed Reissner’s 
fibre in members of several different classes of vmrtebi'ates, and 
admitted that it must l)e accepted as a pre-formed structure to 
be found in all classes of vertebrates from the birds down- 
wards. He figured the fibre in tr.insverse section in the 
spinal cord of Proteus and Siredon, and called attention to 
the widely divergent views upon the nature of the fibre 
which had recently been expressed by Studuicka, Sargent 
and Kalberlah. 
In 1903 there appeared a .short paper by Sargent (’03) 
dealing with the ependymal groove (sub-commissural organ). 
He stated that this serves merely as an attachment plate or 
anchorage for Reissner’s fibre, and omitted all reference to 
Dendy’s paper (’02). He remarked that this structure, while 
present in all vertebrates, is conspicuous in Cyclostomes, 
Selachians and reptiles, less prominent in Teleosts, birds and 
amphibia, and inconspicuous in mammals. As has since been 
shown (Dendy and Hicholls, ’10), the last part of this state- 
ment (if we except the Pi-imates) is entirely erroneous. 
