428 
PROFESSOR POUCHET. 
therefore, to a certain extent opaque. This character 
belongs to it alone ; under the influence of the same reagents, 
the amorphous matter in other parts of the body of 
Amphioxus remains hyaline, and the layers of fibres 
become stained bright red.^ 
In certain cases (fig. 5) a very clear and definite stratifica- 
tion of the amorphous matter may be seen in the papilla. The 
peripheral portion and the base are clearer and less opaque 
than the central portion, and the boundary between these 
ditferent portions is clearly marked out. The central portion, 
which is also the darkest, rests on the layer of transverse 
fibres, and is raised up against the partitions of the cavities 
to where the endothelium is reflected. 
In the centre of the papilla this dark zone presents a 
large projection, wdiich itself may be surmounted by an 
intermediate zone. 
V. — What histological and morphological signification 
can be attributed to the papilla and to the containing 
cavity ? 
The papilla evidently belongs to the category of connective 
or laminar organs. 
The amorphous substances are everywhere very abundant 
in Amphioxus. In transverse sections (fig. 4) two thick 
layers [d, e) of greenish amorphous substance, hyaline and 
devoid of laminar fibres, may be distinguished on each side 
of the median aponeurosis. Elsewhere the amorphous sub- 
stance is very dark g), and contains thick fibres,^ and 
although no part is so opaque as the papilla, it is evident 
that it is a simple variety of connective-tissue, characterised 
by the absence of cellular elements, the great scarcity of fibres, 
and lastly, by the probable presence of a certain quantity of 
fatty matter in a finely divided state. 
The meaning of the cavity which surrounds the papilla is 
also evident. It is a space which is more developed than 
the rest, and which tends to take on the character of a 
serous sac. Silver nitrate gives the same result as on 
serous membranes ; in the only preparation we have made, 
the network of silver staining is very clear upon the lateral 
walls of the cavities, but does not show upon the papilla, 
but no doubt could be obtained there also by employing 
suitable methods. 
^ After the more prolonged action of osmic acid and alcohol the papilla 
becomes darkly coloured, and certain coloured oily globules appeared to 
be emitted by it. This seems to indicate the presence of fatty bodies 
in its composition. 
• Comp. ‘ Ant. Schneider, loc. cit., p. 7. 
