No. 7.— The Segmentation of the Nervous System in Squalus’ 
acanthias. 
brate Head.! 
CONTENTS. 
Pago 
Introduction . . . 148 b. Relation of Encephalomeres 
Criteria of Segmentation ` “148 to Somites . 
Summary of Results of former Inves- 
tigations on the vee eat of 
the Encephalon . . . 150 
I. Locy’s ‘‘ Neural Segments” or 
““Metameres ” . 154 
a. Material . . . 154 
b. Method of Study . + 155 
c. Description of Locy’s ** Neu- 
. ral Segments” . . 156 
d. Continuity of the “ “ Beg- 
ments”. . . 159 
e. Interpretation of the Evi- 
dence. + . 161 
f. Limit of “ Cephalic Plate” . 162 
I. The “ Hindbrain Neuromeres”? in 
S. acanthias . 166 
a. sc sabe of the Term ' ur Neu- 
romere” . . 166 
b. Development of Hindbrain 
Neuromeres + 167 
c. Summary . < 172 
III. The Neuromeres in the Tr unk Re- 
gion . BE eee . 173 
a. Development of Myelo 
meres » o 179 
b. Summary . « 176 
IV. The Neuromeres anterior to the 
Hindbrain . k 177 
a. Essential Criteria of Neuro» 
meres EU 
b. Development of the Fore- 
brain and Midbrain , . 179 
c. Summary . . 185 
V. The Relation of Nimrod to 
Somites . . 186 
a. Relation of Myelomeres % 
Somites . 186 
o, Somatic Value of the Pre-otic 
Mesoderm Segments 
d. Summary i 
VI. The Relation of Neuromeres to 
Nerves . ars 
a. Historical Review - N ` 
b. Nerve Relations in the 
Trunk of $. acanthias . 
c. Nerve Relations in 
Cephalic Region . 
d. Development of the 
1. Oculomotorius 
2. Abducens . 
3. Trochlearis 
VII. Segmental Value of Hindbrain 
Neuromeres 
a. Non-phylogenetic Intrpre- 
tation . . 
b. Phylogenetic Ai 
c. Interpretation of Hindbrain 
Neuromeres in S. acan- 
the 
A Contribution to the Morphology of the Verte- 
By H. V. NEAL. 
Page 
thias . . 245 
VIII. Primitive Relations ot Cephalic 
Segments I.-VII. . 254 
a. Encephalomere VIT. . . 254 
b. Encephalomere VI. . 255 
c. Encephalomere V. . 255 
d. Encephalomere IV. + 256 
e. Encephalomere IIT. 258 
f. Encephalomere II. 258 
g. Encephalomere I, . 259 
h. Comparison with ‘the Sog. 
mentation of Amphioxus . 260 
i, General Conclusions . . 268 
EAr DUMMA a eG kN . 275 
Bibliography . 279 
Description of Plates . 293 
1 Contributions from the Zodlogical Laboratory of the Museum of Comparative 
Zoology at Harvard College, under the direction of E. L. Mark, No. LXXXIX. 
VOL. XXXI. — NO. 7, 1 
