or each arm at its tip, but in thin ophiuran,and the 

 same is truo of Antedon,the formation of the tenta- 

 cles begins in a centripetal manner; that is, the 

 second pair of tentacles appears, not between the 

 end tentacle and first pair but, between the first 

 pair and the ring canal. 



This second pair of tentacles is the rudiment 

 of the buccal tentacles and although differing in 

 function and position in the adult from that of the 

 foot tentacles is never the lass entlrly homologous 

 with the latter. This homology is shown by their 

 origin and the fact that for a time after forming 

 they are directed away from the mouth toward the 

 end of the arm just as ia the case with the foot 

 tentaeles. After a time however, as will be seen 

 later, they turn bock and point toward the mouth 

 thus showing that in this second pair of outgrowths 

 from the radial canals we have to do with the first 

 pair of buccal tentacles of the adult: After buding 

 as ivo see from ths radial canals they migrate to a 

 position on the ring canal with which we find them 

 connected in the adult. 



In "E" the buccal tentacles have no ectodermal LtoOf 



