BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
I. Locy's “Neural Segments” or “Metameres.” 
a. MATERIAL. 
Much of my material was collected with a view to the study of the 
“neural segments” or “metameres ” described by Locy (94 and *95). 
In a preliminary paper, which appeared with numerous illustrations in the 
“ Anatomischer Anzeiger,” 1894, Locy affirmed the discovery of “neural 
segments” in embryos of Squalus acanthias! at stages preceding the 
formation of the medullary 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.” This discovery is interesting, and, if 
confirmed, one of most fundamental importance. I have therefore col- 
lected a large number of Squalus embryos in early stages of develop- 
ment, in order to confirm, if possible, Locy’s results. 
S. acanthias is abundant along the coast of Massachusetts in early 
summer, and the embryos are very easily obtained. My collecting was 
done at Rockport, Massachusetts, during the months of July and August, 
1894, 1895, and 1896, and the number of specimens obtained exceeds 
twenty-five hundred. Locy has well insisted on the necessity of abun- 
dant material in closely connected stages of development. 
The killing agents which I have used were (1) Davidoff’s corrosive 
sublimate-acetic ; (2) Kleinenberg’s picro-sulphuric (undiluted); and (3) 
a mixture of Kleinenberg’s picro-sulphuric (1 vol.), with 3% chromic 
acid (3 vol.), especially recommended by Locy. 
In this material were more than two hundred and fifty embryos 
corresponding to Balfour’s stages C, D, and E. The specimen which 
shows Locy’s “neural segments ” best was killed in Kleinenberg’s picro- 
sulphuric mixture (Plate 1, Figs. l and 2). I cannot recommend the 
mixture composed of picro-sulphuric and chromic acids, since specimens 
killed in it were not well preserved histologically. Davidoff’s corrosive 
sublimate-acetic seems to me the best for general purposes of all the 
killing agents I have used, and consequently most of my material has 
been so killed. For the special study of the development of the nerves 
and the fibre courses in the wall of the brain, I have used material killed 
with vom Rath’s fluid, followed by pyroligneous acid. This method I 
regard as most valuable, since with it nerve fibres are differentiated by 
1 Squalus acanthias (Linnaeus, 1748), synonymous with Acanthias vulgaris 
(Risso, 1826). 
