426 
PROFESSOR POUCHET. 
‘^system of canals’^; it is very different from a capillary 
system properly so called, and its true nature has 
been very variously interpreted by different authors. In 
the neighbourhood of the notochord these cavities appear 
to enlarge and spread out. Fig. 3 b shows one of these 
cavities, pyriform in shape, the extremity being narrowed 
and ^running into a rod, which binds it to the network. 
Thus, this sort of hollow swellings forms a transition to 
other cavities which are quite separate from the network of 
cells, and which we are about to describe. 
ly. The upper surface of the anterior extremity of the 
notochord presents isolated groups of connective-tissue 
cells, which completely envelope the cavities which they 
bound, being arranged in a single row, as in the swellings 
of the network in the neighbourhood of the mouth. 
These groups of cells, always clearly bounded on the 
outside, are generally oval in form, or rather, polyhedral, 
where they are crowded together. The nuclei presents 
slight prominences in their interior, and, in certain 
individuals the cells contain various pigment granules of 
a reddish colour.^ 
The interior of the cavity is filleff with a liquid, which is 
unacted on by osmic acid, and does not stain with most 
reagents. It appears to be watery. The further we recede 
from the extremity of the cord the larger do these laminar 
cavities become (see fig. 2). They become also slightly 
modified, and finally constitute the organs described under 
the very bad name fin rays ” (see figs. 4 and 5). The 
structure of these organs is extremely siniple. They 
are cellular spaces, larger than the others, almost cubical 
in form, one wall of which, that which looks towards 
the notochord, is invaginated into the interior of the cavity 
itself, so as to fill up two thirds or three fourths of it. We 
call the invaginated portion the papilla. It is made of a 
structureless substance, presenting special characters which 
clearly distinguish it from that of the sub-dermic layer. 
Stieda describes these parts very incompletely. He states, 
it is true, the analogy between these cavities and the system 
of canals, and describes their cellular covering, but the in- 
vaginated portion which Muller had already mentioned he 
has overlooked. Muller states that in the interior of these 
cavities there exists eine durchsichtige Fliissigkeit und eine 
consistentere, aber weiche Masse. The cavities are bounded 
at the sides and below by the subcutaneous aponeurosis, 
^ Spme specimens of Amphioxus present a reddish tint, others a 
grcenisli. 
