544 DB. CAKPENTEE'S EESEAECHES ON THE FOEAMINTFEEA. 



ments ; and I am therefore strongly disposed to believe that Professor MAX. SCHULTZE 

 must have been misled by appearances when he stated (op. cit. p. 65) that various other 

 parts of the septal plane are marked by similar pores, more particularly as his figures 

 of the decalcified body do not show that any other threads or stolons of sarcode pass 

 from one of its segments to another, than those just described. 



187. So far, then, the structure of this comparatively gigantic type of Polystomella 

 accords very closely with that of the more delicate species so well described by Professor 

 WILLIAMSON. I have now, however, to give an account of a remarkable feature in its 

 organization, namely, its highly developed canal-system ; which, though not entirely 

 wanting in P. crispa, is so imperfectly presented there, that Professor WILLIAMSON may 

 well be excused for having overlooked it, especially when it is borne in mind that at that 

 period the existence of such a system in Foraminifera was altogether unknown. The 

 general arrangement of this canal-system may be most readily apprehended from an ex- 

 amination of the delineations of the internal casts given in Plate XVIII. figs. 12, 13 ; for 

 the infiltrating substance which has penetrated the chambers has also found its way not 

 only into the main trunks, but also into the minute ramifications of this system, and has 

 thus given just that representation of their distribution and relations, which is afforded in 

 regard to the blood-vessels of the higher animals by a well-injected and clearly dissected 

 anatomical preparation. We observe, in the first place, that in each of what may be 

 termed the two polar regions of the spheroidal body, there is a continuous spiral canal 

 (fig. 12, d, d\ d 2 ), which overlies the extremities of the segments. These two spiral canals 

 (which, although so widely removed from each other, are obviously homologous with 

 the two spiral canals of Operculina, ^f 159) communicate with each other by a very 

 regularly disposed series of canals which pass in a meridional direction between the 

 adjacent external margins of the segments (e, e\ e*). And each of these meridional 

 canals gives off, in its course from one polar region to the other, a uniform succession 

 of pairs of short passages (/,/',/ 2 ) that diverge from each other widely, one series 

 inclining backwards over the uniform anterior margin of the segment next behind it, 

 whilst the other series passes forwards in the intervals between the " retral processes" 

 of the segment next in front of it. The passages which thus diverge from the meridional 

 canals of the outer whorl speedily debouch at its surface ; but if we examine into the 

 termination of those appertaining to the inner whorls (which is best seen in such frag- 

 ments as the one represented in fig. 13), we find that they become continuous with 

 the stolons of the whorl which surrounds them, as is shown at c, c 1 , fig. 12. Further, 

 it may be perceived that each of the meridional canals receives branches from the canal- 

 system of the segment internal to it ; this point, however, can be more clearly made out 

 in sections of the shell. 



188. The spiral canals are frequently brought into view for part of their course, by 

 sections of the shell that pass through it in a direction parallel to the equatorial plane, 

 but at no great distance from one of the lateral surfaces. Such a section, passing over 

 the chambers of the inner whorls, is shown in Plate XVII. fig. 5 ; where we see the 



