424 
PROFESSOR POUCHET. 
section to be finely striated as in fishes. A lamellar struc- 
ture must be attributed to it^ and elongated nuclei appear in 
certain places. It belongs to a system of fibrous tissue widely 
distributed in the body of the animal ; this is quite distinct 
from the laminar system properly so called, while in its 
physico-chemical characters it approaches the dermis. To 
this system belong the aponeuroses which separate the muscles 
and envelope the medulla, &c. The skin, the subdermic apo- 
neurosis, and the fibrous partitions of which we have been 
speaking, when treated with osmic acid and picrocarmine, 
take a splendid red staining, while the structureless sub- 
stance of the subdermic layer and other varieties of struc- 
tureless substance which are sometimes found in the body of 
Amphioxus, remain uncoloured or become slightly yellow, 
but do not take the carmine. 
III. We have said that the special character of the formed 
elements of the laminar tissue of Amphioxus was that they 
are never present in an isolated state nor as cells simply 
united, like the cells in the cornea of Amphibia, by fine 
prolongations. We shall first describe these elements and 
the network which they form in the lophioderm *of the 
caudal fin of Amphioxus, and afterwards their modifications 
in other parts of the body of the animal. 
The caudal lophioderm ” presents a network with regular 
elongated meshes, which had already attracted the attention 
of M. de Quatrefages, and which at once calls to mind the 
figure which he gave at a time when the technical methods 
necessary for such a study were not yet in vogue. 
This network is arranged in one plane in the centre of 
the lophioderme, which is very thin in this region. The 
meshes of the network are elongated in the neighbourhood 
of the anus, and measure 60 ju to 80 /x in length, by 10 /x 
in breadth (see fig. 1). The substance of the network is 
formed of rods, which measure generally 8 to 10 /x .; they 
may, however, be narrower or broader than this. They are, 
in the region of which we are speaking, flattened out ; they 
are solid. At the intersections of the network there are 
generally 6 to 10 larger or smaller nuclei. These are oval 
or almost spherical, irregularly placed, and separated by a 
distance which is generally less than their diameter. Some- 
times several are placed in a row in one of the rods. They 
are then generally more or less obliquely placed. The rods 
after the action of osmic acid stain slightly with picrocar- 
‘ Lophioderm is the termed used by M. Pouchet for the dermal fold 
which forms the substance of the median fin in Ampliioxus and in Am- 
phibia. — Eu, 
