GENERAL CHARACTERS OF FORAMINIFERA. 483 



these Animals was entirely unknown, ranked them under that 

 class. As such they were described by M. D'Orbigny (to whom 

 we owe much of our knowledge of this group), in all his earlier 

 publications ; and they were distinguished from the ordinary 

 Cephalopods that possess a single Siphon passing from chamber to 

 chamber, by the designation Foraminifera, which originally im- , 

 ported that the communications between the chambers are com- j 

 monly made by several such apertures, though it is now more com- 

 monly understood as applying to the sieve-like structure often 

 presented by the external shell. It was by M. Dujardin, in 1835, 

 that the structure of these animals was first shown to be conform- 

 able to the Rhizopod type ; and notwithstanding the opposition to 

 his views which was set-up by Prof. Ehrenberg (who associated 

 them with Bryozoa, Chap, xiii.), they have been confirmed by all 

 subsequent observers, and more especially by the researches of 

 Prof. Schultze,* who has given admirable descriptions of the ani- 

 mals of several different kinds of Foraminifera, derived from 

 observation of them during their living state. The essential con- 

 formity of the Foraminifera to the ordinary Rhizopod type is best 

 seen in such simple forms as Lagena (Plate xv., Fig. 9), in which 

 there is no multiplication of chambers ; for these, which are 

 termed Monothalamous or ' single-chambered,' hold the same place 

 in the Order Eeticularia, that Arcella and Diffiugia (Fig. 235) hold 

 in the Order Lobosa. 



367. By far the greater number of Foraminifera are composite 

 fabrics, evolved by a process of continuous gemmation, each bud 

 remaining in connection with the body by which it was put forth; 

 and according to the plan on which this gemmation takes place, 

 will be the configuration of the composite body thereby produced. 

 Thus, if the bud should be put forth from the aperture of Lagena in 

 the direction of the axis of its body, and a second shell should be 

 formed around this bud in continuity with the first, and this pro- 

 cess should be successionally repeated, a straight rod-like shell 

 would be produced (fig. 10), having many chambers communicat- 

 ing with each other by the openings that originally constituted 

 their mouths ; the mouth of the last-formed chamber being the 

 only aperture through which the sarcode-body, thus composed of a 

 number of segments connected by a peduncle or ' stolon ' of the 

 same material, could now project itself or draw-in its food. The 

 successive segments may be all of the same size, or nearly so, in 

 which case the entire rod will approach the cylindrical form, or 

 will resemble a line of beads ; but it often happens that each seg- 

 ment is somewhat larger than the preceding (fig. 11), so that the 

 composite shell has a conical form, the apex of the cone being the 

 original segment, and its base the one last formed. The method of 

 growth now described is common to a large number of Foraminifera, 



* " Uber den Organismus der Polythalamien (Foraminiferen)," Leip- 

 zig, 1854. 



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