134 FAMILY MILIOLIDA. 



extension of the sarcode-body (which probably occupies the whole cavity of the cj'linder) 

 through the thick layer of solid shell-substance that ensheaths the chambered portion. 



195. In what we may consider the simplest form of B. ci/Undracea, represented in Plate 

 X, fig. 20, the wall of the cylinder is but little thicker than the length of the chambers ; the 

 solid sheath and the " interspace-system" being but slightly developed. The relative position 

 of the chambers is the same as in B. reticulata ; but instead of each chamber opening at once 

 into the general cavity of the cylinder, it is received into a "junctural space" (an arrangement 

 of which we have already seen an indication in D. reticulata) ; and these "junctural spaces" 

 form annular rows of large open mouths upon the interior of the cylinder (as in fig. 24). 

 The large "junctural space" terminates where it embraces the nipple-shaped aperture of 

 the chamber, just in the manner that the vagina terminates where it receives the cervix uteri ; 

 but instead of being a closed cul-de-sac, it gives off a radiating series of tubular passages (fig, 

 22, b, h) which pass towards the surface in close proximity to the proper wall of the chamber 

 (as in fig. 24), and terminate there in the funnel-shaped depressions already mentioned. 

 This condition presents itself only in small specimens, in w-hich the number of chambers 

 in each annulus does not much exceed that which we meet with in D. unnulus and B. reti- 

 culata. Some of these specimens are differentiated by the presence of a circular gallery 

 passing between each annulus of chambers and the internal margin of the cylinder-wall 

 (fig. 20 B, «, a), so as to connect with each other all the "junctural interspaces" of the same 

 annulus ; and it is easy to see how such a gallery may be formed by an endogenous addition 

 of shell-substance, arching over a furrow left at the junction of the annuli (as in B. reticulata, 

 \ 192), and thus inclosing a stolon of sarcode which (as there is strong analogical reason 

 to suppose) would unite together the separate radiating stolons proceeding to the chambers 

 through the "junctural interspaces." But further, in the larger and highly developed specimen 

 of which a portion is represented in fig. 24, a, we find this coalescence still more complete ; for 

 the pouting orifices which project into the general cavity of the cylinders open at once into a 

 wide gallery (shown in vertical section at a , a, and in horizontal section at a, a, a) of uniform 

 diameter throughout ; whilst on the peripheral side of this gallery there are a number of small 

 apertures, of which some lead to the chambers b, b, whilst others (of which there seem to be 

 two to each of the preceding) form the commencements of the " interspace-systems " of di- 

 verging canals cl, d, that terminate in the funnel-shaped cups c, c, on the surface of the cylinder. 



196. Returning now to the simpler type in which the internal orifices of the "junctural 

 intei'spaces " remain distinct, we find that the diameter of the cylinder may be greatly 

 augmented by exogenous deposit around the chambered portion, so as to add a solid wall of 

 great thickness to its exterior. The whole thickness of this wall is traversed by the " inter- 

 space system " of passages, which end on its surface in the ordinary mode ; these passages do 

 not ramify or divaricate, so that their number does not augment as they diverge from each 

 other radially ; but in proportion to the separation which thus takes place between their 

 surface-terminations, the diameter of the cup-shaped depressions increases. In the specimens 

 ■which are distinguished by the greatest development of this exogenous deposit, a most 

 remarkable modification presents itself in the position of the chambers ; for instead of lying 

 on the peripheral side of the internal orifices of the "junctural interspaces," they are disposed 



