2 22 THE AMERICAN MUSEUM JOURNAL 



1. General Structure, 



2. The Canal Systems, 



3. The Skeleton. 



I. General Structure. 



This is best shown by the description of a simple sponge in 

 which the general characteristics of the subkingdom predominate, 

 unmodified by special conditions. 



FIQ. 7-— AN EXAMPLE OF THE BRANCHIN3 HABIT 



The simplest, most primitive, and at the same time most 

 typical sponge is Ascetta primordialis, first described by Hackel 



