DESIGN IN THE ORGANIC WORLD. 



455 



Fig. VII. 



Diagrammatic representation of the 

 transition from the " simple " to the 

 " complex " plan of growth, as shown 

 in vertical section, from the primordial 

 and circumambient chambers {c p c') of 

 the centre, to the margin, whose pores 

 are shown at mp. The chambers ;;/, 

 wS m'^, m^, m^, are all formed upon the 

 smple type (as in Fig. IV., 4), and 

 show at ac, ac, the cross sections of 

 the annular canals, which connect all 

 the chamberlets of one ring, and at 

 r, r, r, the radial passages connecting 

 the successive annuli. The chambers 

 d, d^, d^, are formed upon the duplex 

 type ; the annular canals, ac, ac, being 

 single, but the radial passages r being 

 double. The chambers e, e\ show two 

 annular canals ac, ac, between which 

 is interposed a columnar chamberlet, 

 continuous with the two superficial 

 chamberlets s s'. In the chambers /, 

 f^,p,p, to the margin, which are all 

 formed on the fully-developed complex 

 type, the upper and under superficial 

 chamberlets ss,s' s', are completely cut 

 off from the intermedi-ite columnar 

 portion, and, by a shifting of their 

 position, each is made to communicate 

 with two annular canals. 





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