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and (3) to note the relation of the neuromeres to the sensory and 
motor nerves, to the mesodermal somites, and to the visceral arches. 
I shall begin with a description of the first appearance of neural seg- 
mentation in the embryo. 
1. Locy’s “Neural Segments” or “Metameres”. 
In a preliminary paper which appeared with numerous illus- 
trations in the Anat. Anzeiger in 1894, Locy affirmed the discovery 
of neural segments in embryos of S. acanthias at stages preceding 
the formation of the neural folds and “before the mesoblast has to 
any extent, become divided into somites”. He therefore believed 
that these “epiblastic segments” must be independent of any formative 
influence of the segments of the mesoblast. In his final paper (95) 
he qualified his statement that the segmentation is exclusively epi- 
blastic, since he had meantime discovered in sections that it may be 
found in both mesoderm and ectoderm. He therefore concludes that 
the segments seen in surface study are the remnants of a primitive 
metamerism of the Vertebrate body. He traces the ectodermal seg- 
ments, established in this very early stage “in unbroken continuity 
until they become the neuromeres of other observers”. In the con- 
clusion of his preliminary paper he writes, “no one is likely to 
question but what the segmented condition I have described represents 
a survival [of an ancestral segmentation].” 
In search of evidence to support this phylogenetic interpretation, 
he has studied the early stages of Torpedo, Amphibia and the chick. 
Torpedo embryos are found “not so favorable for the study of the 
segments as acanthias”, yet “the number [of Segments] in a given 
region in Torpedo corresponds to that in S. acanthias”. In the three 
Amphibian forms which Locy has studied (Amblystoma, Diemyctylus 
and Rana) “there are about ten pairs of segments in the broadly 
expanded neural folds of the head”. In the chick “there are eleven 
segments in front of the first formed protovertebra”. Locy has also 
found that in the chick “the walls of the primitive groove are divided 
into segments similiar to those which appear in the neural folds”. 
My own observations in 8. acanthias and Amblystoma differ from 
those of Locy and consequently my interpretation of his “neural seg- 
ments” or “metameres” is different. In agreement with him I find 
the so called segments in the region of the cephalic plate most clearly 
marked in embryos with six to six and a half somites (a stage 
between BALrour’s stages C and D). I find the “segments” confined 
to “marginal bands” along the edges of the neural plate. An exa- 
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