4.58 BERTRAM H. WATERS. 
glosso-pharyngeal nerves, and it is possible that the earlier 
constrictions may potentially correspond to so many nerve- 
roots.” Quite recently, Béraneck (4,@) in Amphibia, and 
Kupffer (16,a) in Teleostean and Cyclostome fishes, have ob- 
served and treated these folds as having segmental value, the 
latter enumerating eight segments or metameres in the hind- 
and mid-brains, and noting their resemblance to similar struc- 
tures in the spinalcord. In a later paper Béraneck (4, 0) gives 
details of the neuromeres (replis médullaires) in the Chick, 
assigning to each a segmental value. His observations of the 
nerve relations to them are substantially those given by Orr 
(21), except in regard to the fifth, which he considers, as does 
Miss Platt (22), to be derived from the first and second of the 
hind brain neuromeres, and the result of two primitively in- 
dependent nerve trunks. Moreover he does not agree 
with the later investigators in homologising neuromeres and 
myelomeres, i. e. similar constrictions in brain and cord. In 
1887 Orr (21), while investigating the embryology of the 
Lizard, figured and described six folds in the hind-brain, five of 
them of equal size ; the sixth, from which the tenth nerve arose, 
somewhat larger. In describing them he used the name 
“ neuromeres,” a word somewhat differently applied by Ahlborn 
(1). Orr has observed— 
(1) That each neuromere is separated from the adjacent one 
on either side of it by an external dorso-ventral constriction 
aud an internal dorso-veutral ridge, each having between these 
limits a semicircular or half-oval appearance : 
(2) That these constrictions or neuromeres are perfectly 
regular and opposite on both walls of the brain: 
(3) That the elongated cells of which they are composed are 
situated radially to the inner curved surface of each neuro- 
mere, and that their nuclei are generally nearer the outer, 
approaching the inner surface only toward the apex of the 
ridge: 
(4) That the cells are confined to their respective neuro- 
meres, so that one structure does not insensibly pass into the 
next succeeding, but is separated from it by a more or less 
