492 Miscellaneous. 
Very closely allied to D. substriatus ; but, besides being nearly 
double the size, it differs in having the thorax less convex, with a 
slight impression on the disk, the sides are less arcuate and more 
distinctly margined, and the posterior angles are much more diver- 
ging. The elytra are more distinctly broader than the thorax, 
more evidently striated ; and, lastly, the pubescence on the head and 
. thorax is more erect and darker in colour. 
Hab, Formosa, 
British Museum, 
May 15, 1878. 
On the Organ called “ Dorsal Chord” in Amphioxus lanceolatus. 
By MM. J. Renavr and G. Ducuame. 
In the Vertebrata the tissues of the skeleton may be divided into 
three principal categories:—1, the primary axis, formed by the 
dorsal chord; 2, the cartilaginous tissue; 3, the osseous tissue. 
These different tissues succeed one another in the higher animals, 
and the definitive skeleton is formed by bone, or at least by true or 
calcified cartilage. At this period there only remain rare vestiges 
of the primary axis or dorsal chord; so that, except Amphiovus, we 
know of no Vertebrate of which the definitive skeleton is repre- 
sented solely by a persistent notochord. 
This organ, moreover, possesses in the series typical characters 
which it is necessary to refer to briefly; it is formed of globular 
cells, soldered to one another after the fashion of epithelia, as trans- 
parent as glass, and possessing a very distinct nucleus (usually 
thrown back to the periphery). 
The dorsal chord of fishes does not differ fundamentally from that 
of the embryos of the highest Mammalia. That of Amphioxus, on 
the contrary, presents no arrangement resembling the structure 
just described. It is contained in a cylindrical sheath which en- 
velops it on all sides ; and, in sections made perpendicularly to the 
general axis of the body, after hardening in dextrine and alcohol, it 
proves to be constituted as follows :— 
In the interior of the sheath, stretched horizontally from the left 
to the right side, are seen some fibres of uniform diameter, cylin- 
drical, solid, and adhering by their extremities to the general en- 
velope. In proportion as they approach the dorsal surface these 
fibres curve gently upwards, so as to circumscribe in the median 
line, between the sheath and the chord, an empty spindle-shaped 
space. On the ventral side the same arrangement is repeated in the 
opposite direction ; so that only the fibres of the middle plane are 
horizontal and rectilinear. 
In a longitudinal section passing through the axis of the chord 
and the two sides of the body the sheath is shown divided in the 
direction of its length ; and the area thus intercepted is occupied by 
the fibres of the chord, which consequently offer a scalariform ar- 
rangement relatively to the two margins of the sheath. 
In such a preparation, suitably coloured by means of picrocarmi- 
nate of ammonia or of eosine dissolved in water, we observe the fol- 
lowing details :— 
