PLATE XIV 



ONTOGENY AND PHYLOGENY OF THE TEREBRATELIJD.E 



Figures represent bracliial supports in various stages of growth in dif- 

 ferent genera and species. All are drawn of apj)i'oximately the same 

 lengtli to facilitate comparison, so that in general the younger stages are 

 much enlarged. Vertical rows of figures connected by dotted lines indi- 

 cate ontogeny as far as known. Horizontal rows indicate the same 

 growth-stages of higher forms and the adult structure in genera repre- 

 senting these stages. All figures are of recent species unless otherwise 

 stated. 



Morphogeny of Megathyrin^ (Page 300) 



Figure A. — Early larval brachiopod without calcified brachial sup- 

 ports, but with circlet of centripetal tentacles on the lophophore. The 

 gicyniform stage. 



Figure Aa. — Givynia capsula Jeffreys ; a morphic equivalent of larval 

 stage, figure A. 



Figure B. — Later immature stage of A ; showing growth of septum, 

 aiul consequent introversion of edge of lophophore. Early ci.ttellifonn 

 stage. 



Figure Ba. — Zellania liasinn IMoore, from the Lias; a morphic 

 equivalent of figure B. 



Figure Bi. — Cistella nenpolitana Scacchi ; showing calcification of 

 loop attached to septum, and other adult features. 



Figure Bj. — Megathj/ris decollata Chemnitz; adult shell; showing 

 advance over Cistella in the two lateral septa, thus increasing the length 

 of the loop. 



Morphogeny ok Dallinin^e (Pages 295-299) 

 Ontogeny of Macandrevia cranium Miiller 



Figure A. — Givyniform stage. 



Figure B. — Cistelliform stage. 



Figure Ci. — Platidiform stage ; showing union of descending lamoUai 

 with dorsal septum. 



Figure Ci'. — Side view of septum of jtrecediiig. 



Figure Di. — More advanced j)lali(lijbr7n stage; showing growth of 

 ascending branches, or secondary loop. 



Figure I)i'. — Side view of same. 



Figure Ei. — Ismcniform stage, with ascending branches still attached 

 to septum. 



Figure Fi. — Muhlfeldtifnrm stage; showing holes in ascending 

 lamella; as in Miihl/eldtia, figure Fa. 



