16 
GKOEGIO E. NICIIOLLS. 
In tlie same year still anotlier work by Sargent appeared 
(’03a), dealing primarily with the torus 1 o n gi t u d i u al i s , 
which he this time correctly identified. In this he gives a 
full historical survey and a description of the condition of 
this organ in a number of Teleosts. He points out the 
several errors into which different observers have fallen in 
attempting to homologise this structure, peculiar to Teleosts, 
with various parts iu the brains of other vertebrates, but 
a,ppears completely to overlook the fact that he himself had 
confused the torus 1 on gi t udi n al i s with the posterior 
commissure! lie accepts Rabl-Ruckhard’s (’81) disproof of 
the earlier theory that the torus is the homologue of the 
fornix of higher vertebrates, but denies, rightl}'^ enough, 
that the latter author is correct in supposing that it is 
homologous with the sub-commissural organ (“ependymal 
thickening”), pointing out that in Teleosts both of these 
structures co-exist. 
Sargent himself, however, falls into fresh error, as I believe, 
in stating that the torus is the homologue of the “ Dach- 
kern ” or roof-nucleus of other vertebrate classes. He claims 
that he has succeeded in tracing from the cells of the torus 
thi’ee separate fibre-Hacts strictly homologous with the three 
fibre-tracts which he had already traced from the “ Dach- 
kern ” in Selachians. 
I cannot believe that this suggested homology can be 
correct and, on the conti-ary, I shall bring forward evidence 
later in this paper to show tliat the “ Dachkern ” nucleus is 
also present in some Teleosts, and is perfectly distinct from 
the torus. 
In 1904 Sargent published what must be regarded as his 
principal paper (’04) upon Reissner’s fibre, in which he 
collected and amplified the results announced in his earlier 
works. 
In a footnote (p. 158) he refers to Dendy’s (’02) descrip- 
tion of the “ciliated grooves” in the brain of the ammoccetes 
of Petromyzon and Gleotria. He represents that author 
as stating that the cilia of the grooves are longer than those 
