GENUS CAEPEXTEKIA : STEUCTITEE AND AFFINITIES. 567 



other ; but at , a, 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, ), their internal orifices do not show themselves upon the 

 ridges, but are crowded together along their bases (fig. 6, b, and fig. 9). The septa, 

 whether primary (separating the chambers from each other) or secondary (partially 

 subdividing the chambers), are obviously formed by a doubling-in of the outer wall, so 

 as to make each septum consist of two laminae (fig. 12, a, a) ; this is seen also in sections 

 of the incomplete septa (fig. 12, b), as well as of the ridges which may be considered as 

 rudimentary septa (fig. 15, b, b, I}. 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 

 differentiate 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 

 during 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 whorl after another until the original nucleus 

 was arrived at (an operation which has been very dexterously performed for me by my 

 draughtsman Mr. GEORGE WEST); and 1 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 Eotalia 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 



