355 
agreement in the work of BERANECK, KUPFFER, ORR, Mc CLuRE, ZIMMER- 
MAN and WATERS, as to the identity of those in the medulla and their 
relation to the definite cranial nerves in the various vertebrate classes 
from fishes to mammals. 
Until recently, observations on the neural segments had been 
confined to embryos after the closure of the neural groove, and, there- 
fore, they came to be looked upon as structures that follow rather 
than precede the segmental divisions of the mesoblast. But the case 
presented by these segments has been especially strengthened by 
showing (Locy ’93) that they antedate the mesomeres even of the 
trunk region. Locy was the first to trace the early history of the 
neural segments. He found that they make their appearance before 
the mesoblastic divisions, and as his sketches show, traced them through 
the stages with an open, closing and closed neural groove and identi- 
fied those of the medulla with the neuromeres of other authors. 
NEAL ’98, working upon the same material, finds the segments 
described by Locy in the early embryonic stages, but claims for them 
great irregularity, and dissents from regarding them as natural seg- 
ments. Also, basing a conclusion largely on negative evidence — 
failure to find these segments in certain stages — he doubts their 
continuity. Upon this point of continuity my observations on Teleost 
and Chick embryos are unvarying and favor the view that the early 
neural segments are to be identified with the neuromeres. 
A review of the literature upon neural segments shows: 
1) There is substantial agreement among observers as to the six 
segments in the hind-brain, their nerve relation and metameric 
value. When more than six segments have been observed 
(HorrMAnn ’89, Locy ’95) segments caudad to the true sixth 
have been counted. 
2) There are but few observations on the encephalic segments 
that lie in front of the cerebellum. 
The following is an abbreviated statement of observations on the 
neural segments of Teleost and Chick embryos made during 1898 and 
’99 in the zoölogical laboratory of Northwestern University under the 
direction of Prof. Wm. A. Locy. They will be published elsewhere at 
greater length. They show the very early appearance of neural seg- 
ments and their continuity. They show especially well the primary 
segments of fore- and mid-brains in the earliest stages and also the 
modification of these segments up to the time they become obliterated 
by the expansion of the brain walls. 
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