FORAMINIFERA — ORBITOLITE. 443 



plete annulus of sarcode round the margin of the outermost 

 zone ; and it is probable that it is by a deposit of calcareous 

 matter in the surface-portion of this annulus, that the new zone 

 of shelly substance is formed, which constitutes the walls of the 

 cells and passages occupied by the soft sarcode body. Thus we 

 find this simple type of organization giving origin to fabrics of 

 by no means microscopic dimensions, in which, however, there 

 is no other differentiation of parts than that concerned in the 

 formation of the shell ; every segment and every stolon (with 

 the exception of the two forming the " nucleus") being, so far 

 as can be ascertained, a precise repetition of every other, and 

 the segments of the nucleus differing from the rest in nothing 

 else than their form. The equality of the endowments of the 

 segments is shown by the fact, of which accident has repeatedly 

 furnished proof, — that a small portion of a disk, entirely sepa- 

 rated from the remainder, will not only continue to live, but will 

 so increase as to form a new disk; the loss of the nucleus not 

 appearing to be of the slightest consequence, from the time that 

 active life is established in the outer zones. In what manner 

 the multiplication and reproduction of the species are accom- 

 plished, 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 (§ 197), 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 

 develope themselves into new fabrics. Of the mode' wherein 

 that sexual operation is performed, however, in which alone true 

 Generation consists, nothing whatever-is known. 



289. 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 Orbi- 

 tolite, we observe that the marginal pores, instead of constituting 

 but a single row, form many rows, one above another; and be- 

 sides this, the cells 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. "When a vertical section is 

 made of such a disk, it is found that these oblong chambers 

 constitute two superficial layers, between which are interposed 

 columnar chambers of a rounded form ; and these last are con- 

 nected together 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. 208). For the ob- 

 long superficial chambers are occupied by segments of sarcode, 

 e e, d d, lying side by side so as to form part of an annulus, but 

 each of them being disconnected from its- neighbors, and com- 

 municating only by a double footstalk with the two circular sto- 

 lons a a'j b b', which obviously correspond with the single stolon 



