and McBRIDE are due almost wholly to the stages in the 

 metamorphosis selected in each case- for the study of 

 the question; GOTO selectin£ a very late stage when 

 the larva had all' but disappeared t while the stage 

 chosen by McBRIDE is an eerly one in which the rudi- 

 ments of the star are just appearing. 



If the five groups of echinoderms have sprung 

 fromaa common stem after radial symmetry had been es- 

 tablished, then in $ho metamorphosis which is found 

 in all the groups , there should be discoverable a 

 unity of relation between larva and adult. It is 

 hard to conclave of the radial' symmetry of echine 



dependently aquired by each grou-, 

 although it is easy to seehov secondary changes may 

 have arisen in the metamorphosis since the groups sep- 

 arate d . 



The five groups of echinoderms stand isolated 

 one another almost as completely as does the 

 Echinoderm phylum from the other phyla of the animal 

 kingdom and it is not my intention at this time to 

 enter into a discussion of the interrelationships 

 of echinoderms. I wish however to point out an in- 

 teresting series of facts , illu jt/at ed by members of 



