340 Mr. H. B. Brady on Ellipsoidina, 
On exposing the interior of the shell, by carefully breakin 
away the chamber-walls (fig. 4), or on mounting young an 
transparent specimens in Canada balsam, it is seen at once 
that the column extending from the apex of the primordial cham- 
ber (or sometimes from within it) to the anterior of the termi- 
nal segment bears only superficial resemblance to the neck in 
the chambers of the Nodosariv, and is in no way its homo- 
logue :. indeed the description of it in the memoir under notice 
is correct in most of its features. The term ‘ tubular,” as 
applied to it, is apt to mislead; for although in form the column 
is often cylindrical and hollow, the walls have almost invaria- 
bly perforations of considerable size, and are often even split 
up into several smaller and independent portions, Figure 5 is 
a drawing of one of these divided into three spreading arms; 
and in fig. 6 the tendency to separate into several distinct 
members may be well seen. When partaking more of the 
cylindrical or tubular form, a high magnifying-power and 
careful regulation of the light will generally show the existence 
of perforations, longitudinal and slit-like, from which it may 
be inferred that the column consists of delicate lines of shell- 
substance associated in perpendicular bundles. ‘This conclu- 
sion is further strengthened by the frequent occurrence of 
surface-irregularities running in the same direction. When 
the column takes the common and more or less tubular form, 
its apex is usually swollen at the point where it joins the en- 
—— chamber, whilst nearer the base little, if any, altera- 
tion in diameter is observed ; in some instances it tapers regu- 
larly down to the point of junction with the inner chamber. 
The shell-wall is not, as a rule, perforated at either the an- 
terior or posterior extremity within the walls of the column. 
In the exceptional cases in which an orifice occurs in the por- 
tion of the chamber-wall corresponding to the upper end of a 
segment of the central column, it may or may not form the 
channel of communication. But the function of the central 
body is not that of a stoloniferous tube; and when it-performs 
this office (if ever), it arises from casual irregularity in growth. 
The purpose which it serves is, I believe, purely that of a sup- 
port for the chambers, which are otherwise so lightly held 
together that the slightest shake would separate them. The 
adhesion between the posterior portions of the chambers is 
scarcely perceptible, and amounts to little more than the mere 
juxtaposition of surfaces. If Professor Seguenza’s figures be 
drawn from perfect specimens, and not from such as have had 
the outer chamber broken away, it would follow that the sup- 
port is formed before the enveloping chamber, The form of 
the column and its relation to the shell make it improbable 
