1893.] Phylogeny of an Acquired Characteristic. 877 
Fig. 8. A young shell of the same, natural size, with com- 
plete living chamber. 
Fig. 9-10. Coloceras globatum (sp. De Koninck) Hyatt, 
adult. Fig. 9 has a part of the outer shell broken off showing 
the edges of the septal partitions (sutures) as lines on the 
strong cast of the interior. 
Figs. 11-13. Same to show the cyrtoceran stage and section, 
with its impressed zone. 
Fig. 14. 
Figs. 15-16. Nautilus pompilius to show the cyrtoceran 
stage with its impressed zone. 
