Mr. H. J. Carter on the Structure of the Foraminifera. 313 



lated planes of these canals which lie between the planes of the 

 spicules (fig. 1 1 d), the canals of which anastomose with each 

 other through the spicular planes, communicate with the inter- 

 septal canals, and open on the surface of the cord respectively. 



In some, if not in all, specimens the spicules not only exist 

 throughout the cord (for they can be seen on its inner aspect, 

 where the cord is in contact with the outer margin of the cham- 

 bers), but are continued inwards over the interseptal spaces utmost 

 to the centre of the Operculina. 



Now, if the substance of the cord were homogeneous, the 

 structures mentioned in it could not be defined. If it were 

 simply the "peculiar manner" in which its homogeneous sub- 

 stance were " traversed by the set of canals " which it contains, 

 as stated by Dr. Carpenter, then portions of the cord, on trans- 

 verse fracture, could not be made to present the ends of spicules 

 at the fractured points, nor could portions of the cord fall out, 

 on fracture longitudinally, in the form of spicules. Nothing 

 but certain portions of the cord being harder than the rest, and 

 these portions being of a spicular form, could give rise to 

 either of these appearances ; while if it be the " peculiar manner 

 in which the homogeneous substance of which it is composed is 

 traversed by the set of canals " which gives the cord an appear- 

 ance of spicular structure, how is it that this spicular appearance 

 exists over almost all the interseptal spaces of some specimens 

 where there is no plexus, and no canals but a few short ones 

 which pass through it almost perpendicularly ? It is, however, 

 useless to have recourse to argument for conviction when the 

 fact can be demonstrated ; so we will turn our attention to an- 

 other point in the economy of this shell, viz. the " canal-system." 



As regards the use of the canal-system, nothing yet has been 

 definitely assigned. I formerly thought that it subserved the 

 purpose of a water-circulation, as in Sponges, — viz. the water 

 going in by the ends of the small canals which open on the 

 horizontal surface of the test, and coming out through the ori- 

 fices of the larger ones on the surface of the spicular cord ; and 

 I now think that this may be a part of their function, at the 

 same time that they may draw in nutritious particles by the 

 small pores also, like the Sponges. The anastomosing canals, 

 resembling also in appearance and function the mycelium of 

 Fungi, serve to convey portions of the sarcode (upon which the 

 canals themselves are first moulded) to the points from which 

 new portions of the organism are to be developed, while they 

 undoubtedly, too, in part, perform the office of excretory chan- 

 nels ; for in the recent and living specimens of Operculina ara- 

 bica which I obtained on the coast of Arabia, the sarcode of 

 the interseptal canals, after the calcareous matter of the test has 



