442 



FORAMINIFERA, POLYCYSTINA, AND SPONGES. 



senting not the least trace of higher organization in any part, 

 and connected together by " stolons" of the like substance. The 

 " central" pear-shaped segment, a, is seen to have budded off its 

 "circumambient" segment, h, by a narrow footstalk or stolon; 

 and this circumambient segment, after passing almost entirely 

 round the central one, has budded off three stolons, which swell 

 into new segments from which the first annulus is formed. 

 Scarcely are any two specimens precisely alike, as to the mode 



in which the first annulus 

 Fig. 207. originates from the " circum- 



ambient" segment; for some- 

 times a score or more of 

 radial passages extend them- 

 selves from every part of the 

 margin of the latter (and 

 this, as corresponding with 

 the plan of growth afterwards 

 followed, is j)i'obably the 

 typical arrangement), whilst 

 in other cases (as in the ex- 

 ample before us) the number 

 of these primary offsets is 

 extremely small. Each zone 

 is seen to consist of an as- 

 semblage of ovate segments, 

 whose height (which could 

 not be shown in the figure) 

 corresponds with the thick- 

 ness of the disk ; these seg- 

 ments, which are all exactly- 

 similar and equal to one another, are connected by annular 

 "stolons;" and each zone is connected with that on its exterior, 

 by radial extensions of those stolons, passing off between the 

 segments. Although no opportunity has yet been obtained, for 

 a microscopic examination of these animals in their living state, 

 yet there can be no reasonable doubt that the radial extensions 

 of the outermost zone issue forth as pseudopodia from the mar- 

 ginal pores ; and that they search for and draw in alimentary 

 materials, in the same manner as do those of other Foramini- 

 fera ; the whole of the soft body, which has no communication 

 whatever with the exterior, save through these marginal pores, 

 being nourished by the transmission of the products of diges- 

 tion from segment to segment and from zone to zone, through 

 similar bands of gelatinous substance. In all cases in which the 

 growth of the disk takes place with normal regularity, it is pro- 

 bable that a complete circular zone is added at once. Wlien the 

 sarcode body has increased beyond the capacity of its envelopiiii;- 

 disk, it may be presumed that its pseudopodial extensions, pro- 

 ceeding from the marginal pores, coalesce, so as to form a com- 



Composite Auimal of simple lype of OrhitoLUes 

 complanatus : — a, cenlral mass of sarcode; 6, cir- 

 cumambient mass, giving off peduncles, in wiiich 

 originate liie concentric zones of segments con- 

 nected by-annular bands. 



