496 



FORAMINIFERA '. ORBITOLITES. 



zones. In what manner the multiplication and reproduction of 

 the species are accomplished, we can as yet do little more than 

 guess ; but from appearances sometimes presented by the Sarcode- 

 body, it seems reasonable to infer that Gemmules, corresponding 

 with the Zoospores of Protophytes (§ 241), are occasionally formed 

 by the breaking-up of the Sarcode into globular masses ; and that 

 these, escaping through the marginal pores, are sent forth to deve- 

 lope themselves into new fabrics. Of the mode wherein that Sexual 

 operation is performed, however, in which alone true Generation 

 consists, nothing whatever is known. 



379. One of the most curious features in the history of this 

 Animal, is its capacity for developing itself into a form which, 

 whilst fundamentally the same as that previously described, is very 

 much more complex. In all the larger specimens of Orbitolites we 

 observe that the Marginal Pores, instead of constituting but a 

 single row, form many rows one above another ; and besides this, 

 the Chamberlets of the two surfaces, instead of being rounded or 

 ovate in form, are usually oblong and straight-sided, their long 

 diameters lying in a radial direction, like those of the cyclical type 



of Orbiculina (Plate 



Fig. 252. xv -> fi S- 6). When a 



vertical section is 

 made through such 

 a Disk, it is found 

 that these oblong 

 Chambers constitute 

 twosuperficial layers, 

 between which are 

 interposed columnar 

 ch ambers of a rounded 

 form ; and these last 

 are connected toge- 

 ther by a complex 

 series of passages, 

 the arrangement of 

 which will be best 

 understood from the 

 examination of a 

 part of the Sarcode- 

 body that occupies 

 them (Fig. 252). For 

 the oblong superficial 

 chambers are occu- 

 pied by Sub-segments 

 of Sarcode, c. c, d d, 

 lying side by side, 

 so as to form part 

 of an annulus, but 



Portion of Composite Animal of Complex Type 

 of Orbitolites complanatus:—a a', b b', the upper 

 and lower Rings of two Concentric Zones ; c c, 

 the upper layer of superficial Sub-segments, and 

 d d, the lower layer, connected with the Annular 

 bands of both Zones ; e e and e' e', vertical Sub- 

 segments of the two Zones. 



