GENUS CAEPENTEEIA STEUCTUEE AND AEEINITIES. 
567 
other; but at fig. 15, it is seen that in the neighbourhood of the ridges which 
project from the inner wall into the cavity of the chamber, the tubes either bend or 
incline themselves in such a manner, that, whilst their external orifices are pretty 
uniformly distributed (fig. 6, a), their internal orifices do not show themselves upon the 
ridges, but are crowded together along their bases (fig. 6, h, and fig. 9). The septa, 
whether 'primary (separating the chambers from each other) or secondary (partially 
subdi\iding the chambers), are obviously formed by a doubling-in of the outer wall, so 
as to make each septum consist of two laminse (fig. 12, «, «) ; this is seen also in sections 
of the incomplete septa (fig. 12, 5), as well as of the ridges which may be considered as 
rudimentary septa (fig. 15, b, b, b). The two layers sometimes separate from each other, 
as shown in these figures, so as to leave intraseptal spaces ; and these form a tolerably 
regular canal-system, which may be traced throughout the network of ridges that covers 
the inner wall of each principal chamber, and, through the primary septa, into the ring 
that surrounds the vertical canal (fig. 7, g, g’). 
230. Whilst, therefore, the general plan of conformation of Carpenteria seems _to 
difierentiate it strongly from that of the ordinary Foraminifera, so close an alliance to 
them is indicated by the minute structure of its shell, that it becomes of special import- 
ance to determine whether its peculiarities are original, or whether they are acquired 
dming the progress of development. I have fortunately been enabled to determine this 
point by the comparison of several specimens in different stages of evolution, and by the 
removal from the older specimens of one wliorl after another until the original nucleus 
was arrived at (an operation which has been very dexterously performed for me by my 
draughtsman Mr. Geoege West) ; and I can state without hesitation that the early 
condition of this apparently anomalous organism accords with that of the Helicostegue 
Foraminifera generally, — its approximation being the closest to Rotalia in general form, 
but its tendency being rather towards Globigerina in this particular, that its chambers 
do not seem to communicate directly with each other, but that each has a separate 
external orifice directed towards the umbilicus. Various aspects of this first-formed 
portion of the shell, two of them showing the animal substance contained in the 
chambers, are seen in Plate XXII. figs. 2, 3, 4. Now supposing that a Globigerina were to 
grow in such a manner, attached by one of its surfaces, that the walls of its successively- 
formed chambers came into mutual contact, and that these chambers were so shaped and 
so piled one on the other as to give to the entire shell a conical form, each chamber 
opening by its own separate orifice into an umbilical funnel, we should have the 
essential type (so far as its shell is concerned) of Carpenteria', and this is really the 
mode in which the latter type is superinduced upon the former, as the development of 
the organism advances. It is further interesting to observe that the great size of the 
chambers which form the superficial whorl of Carpenteria, has every appearance of 
being due to the deficiency of that complete segmentation, in the later stages of 
growth, which characterizes the earlier ; for every one of the loculi marked out by the 
ridges projecting into the interior corresponds so closely both in size and general aspect 
