316 Mr. H. J. Carter on the Structure of the Foraminifera. 



structure at the base, where the latter are in contact with the 

 spire or spicular cord, — united also with the membranous tubes 

 of the interseptal canals — those of the marginal plexus on both 

 sides, those which unite the chambers themselves together across 

 the interseptal spaces, and, lastly, others which unite the cham- 

 bers with the vertical tubuli which open on the horizontal sur- 

 face of the test. 



Besides this, the chambers have generally been more or less filled 

 with minute, spherical, nucleated bodies, the note of whose size I 

 have mislaid, similar to those which I have described and figured 

 in the freshwater llhizopod called " Euglypha" and which I have 

 considered to be embryonal cells (Ann. Nat. Hist. ser. 2. vol. xviii. 

 pi. 5. fig. 26, and vol. xx. pi. 1. fig. 196, &c.), which, again, arc 

 like those figured by Dr. Carpenter in the cells of Orbitolites 

 (Phil. Trans, pi. 4. fig. 3), and which he views as the sarcodc 

 broken up into propagative " gemmules." My own view of them 

 in Operculina also is, that they are propagative bodies of the 

 species. But the most interesting point which their presence in 

 the chambers of Operculina has elicited with me is that by 

 slight pressure they can be easily made to pass through the 

 short channels of communication which exist between the cham- 

 bers and the interseptal canals, into the latter, — showing thus, 

 as before stated, that one of the uses of the interseptal canals is 

 to give exit to these bodies through the branches of the mar- 

 ginal plexus which open on the surface of the last or outermost 

 turn of the spicular cord. 



The bond of union between the chambers at the spicular cord 

 is not tubular; or, at least, I never saw the propagative spherules 

 pass from one chamber to the other through it, while I am in- 

 clined to think that this bond is chiefly composed of the sarcodal 

 plexus of the spicular cord, and that from this the chambers are 

 developed, as will be better understood presently — also that the 

 part of the plexus which is more directly concerned in uniting 

 the chambers occupies the free surface of the spicular cord, and 

 gives rise to that arched opening which exists between the septa 

 and the spicular cord. The free margin of the septum here also 

 frequently presents a scolloped form, as if it had rested on a 

 plexus of sarcodal filaments, while in some cases I have not been 

 able to distinguish any aperture between the septum and the 

 cord at all, indicating that the two are sometimes in contact. 

 All this seems to show that the chambers are developed from the 

 marginal plexus, and not from each other. 



As regards the function of the chambers, the presence of the 

 nucleated spherules above mentioned in them seems to indicate 

 that they are the reproductive organs; and the fact that in 

 Alvcolina ellipiica they are frequently almost wanting altogether, 



