PREVIOUS INTERPRETATIONS OF CNIDARIA 193 



are few specialized cases only that appear here as exceptions. 

 Thus planulae of Lucernariidae immediately begin to creep 

 over the substratum after they had abandoned their eggs 

 (Fig. 35). No cilia can again be found in young Hydrae 

 which become free during a very advanced state, etc. The 

 primary larvae which live in water (in opposition to the secon- 



Fig. 35. Hatching planula of l^iicernaria sp. (without ciliature). 

 (After Wietfzykowski.) 



dary larvae which become free during a much older onto- 

 genetic state) move by means of cilia, regardless of the phylum 

 the adult form belongs to (the branchiostoma larvae). Even 

 in the ciliation we can observe the w^orking of the general rule 

 that polymerization is followed by an oligomerization with 

 a differentiation, here in the form of localizations, formations 

 of bunches of cilia, circlets of cilia, etc. 



In Cnidaria we can expect a priori a reduction of the general 

 ciliation due to their transition to a sessile way of life, and 



