194 NATURE AND AFFINITIES OF THE SPONGES. 



aDoarent not only in the matured condition of such a form as Phalanstermni 

 —where the collar is rudimentarily developed-but also in the ontogeny 

 or individual life-history of all other collar-bearing zooids and which, 

 whether they belong to the simple and independent Choano-Flagellata or 

 to the interstitial system of a complex sponge-stock, commence existence 

 as similar coUarless uniflagellate monads. 



