OUR BEST FEATURES 



ostracoderms (Fig. 57) the mouth cavity was in 

 series with the cavities of the gill openings and was 

 probably homologous with them. 



The predecessors of the vertebrates probably 

 fed upon small organisms and organic matter, 



Fig. 57. Attempted Restorations of the Mouth and Gill Region 

 OF Two Cephalaspid Ostracoderms by Stensio. 



For details, see p. xxv. 



which were scooped into the mouth cavity and 

 may have been passed along to the stomach by 

 the lashing of cilia located in a groove, as in the 

 living Amphioxus (Fig. 54). 



This method of ingestion by means of cilia may 

 also have been practised by some of the ostra- 

 coderms, the earliest known forerunners of the 



95 



