578 



NEW YORK STATE MUSEUM 



assumption of opposite directions of the new branches. This 

 would furnish eight " secondary branches ". But a material 

 change now takes place in the arrangement of the new thecae, 



c^ 



Fig. 4 Idem. Branches of 

 third order have begun to form. 

 Vertical view. x4 



Fig. 5 Idem. Same growth 

 stage. Sicular view. Shows 

 mode of branching on left 

 side. x3J*£ 



Fig. 6 Idem. A little 

 more advanced stage. 

 Antisicular view of sic- 

 ula. x4 



growing from these eight tertiary thecae. If we give the funicle 

 a horizontal position in the drawing (fig. 7, 8), the four thecae (a) 

 of these eight tertiary ones, which lie on the side of the vertical 

 axis (A-B in fig. 8), produce thecae which do not diverge from 

 their mother thecae, but retain the direction of the latter. This 

 leads to a serial arrangement of the thecae and to the " denticu- 

 late branches " of other authors. The other four tertiary thecae 

 (6) however, which lie subparallel to the funicle, produce a new 



c— 



Fig. 7 Idem. Next growth 

 stage. Differentiation of ar- 

 rangement of thecae has com- 

 menced, a branches with seri- 

 ally arranged thecae ; at b dich- 

 otomy continuing. x2^ Fig> 8 idem. A further advanced growth stage, 



whicb shows more distinctly the differentiation of the 

 tertiary branches (III) and the composition of the four 

 principal stems of thecae (see thecal apertures in upper 

 left quarter). x2^. 



bifurcation. They become thus component parts of the princi- 

 pal stems of the mature colonies. 



Of the eight tertiary branches (marked III in fig. 8) resulting 

 from these bifurcations, those subparallel to the funicle become 

 denticulate, while the others bifurcate again. 



