Williamson on Fanjasina. 
89 
marked tendency to divide into two branches (fig. 3 a, 6), one 
of which is usually in a plane a little above thejother. On 
tracing back these tubes as they proceed from the outermost 
to the inner convolutions, we perceive that the bifurcations, 
which at one time marked the outer extremities of each series, 
serve two purposes : they are designed, primarily, to multiply 
the number of the external orifices ; but in addition to this, they 
subsequently facilitate the establishment of a free communica- 
tion between the internal intra-septal spaces and those of the 
newer convolutions, in which the septa are much more nu- 
merous ; but though a lateral divergent communication is thus 
maintained, I have only seen one instance in which a direct 
lateral communication was established between two transverse 
septa of the same convolution, parallel with the spiral septum. 
The exception is seen at fig, 3 c. In this respect the species 
under consideration differs materially from the forms described 
in my preceding memoirs. The small circular apertures which 
appear along the course of these tubes, mark the points where 
the section has traversed the orifices of the canals descending 
to the inferior surface of the shell. 
Fig. 4 represents a third section made across the points fig. 
1 c c. This section has cut through the shell a little above 
the superior extremities of the cells belonging to the central 
convolutions ; a few of those belonging to the second spiral being 
seen at 4 a. The outermost convolution, on the other hand, 
has been intersected across its large oral (?) apertures (fig. 1 e), 
revealing the nature of the connection (46) that exists be- 
tween contiguous segments. We now see that the portions, 
which in the section fig. 3 had the appearance of large 
radiating tubes, are really the lower borders of vertical 
intra-septal spaces (fig. 4 c c'), which also give off true 
divergent cylindrical canals from their external margins, pene- 
trating the thick parietes of the shell. These spaces extend 
from the top to the bottom of each septum, and only assume 
the form of canals when they approach the peripheral shell 
walls. The connecting branches which unite the spaces of 
different convolutions (fig. 3 b) are also tubular. 
The septa of the second convolution in this section exhibit 
similar intra-septal spaces (4 d), which communicate exter- 
nally, as just described, with those of the outermost convo- 
lution, and also open internally into a large and very irregular 
central cavity (fig. 4 e and 5 p). The true nature of this cavity 
will be better understood on referring to fig. 5, which repre- 
sents a vertical section of this instructive object, passing nearly 
through its centre. I am not quite certain whether it has 
actually traversed the primordial cell, but if not, it has cer- 
h 2 
