BIOCHEMICAL STUDIES OF PHYLOGENY 129 



the variety of phosphagens. It is certain that many new chemicals 

 still remain to be discovered and the biochemical variations will 

 probably be found to be as great as the more obvious morphological 

 variations. 



From the phylogenetic point of view, therefore, the phosphagens 

 are not a great deal of assistance. The table shown on p. 112 

 can now be amended as below. 



The gaps in the table will be filled as more research is done on 

 this subject. 



(2) Sterols 



The phosphagens are not the only compounds that have been 

 used to indicate phylogenetic relationships. Within recent years 

 certain sterols have been used to elucidate relationships, though the 

 work is still at a developmental stage. Some applications of the 

 sterol studies are as follows. 



Hyman (1955) in her volume on the echinoderms does not 

 follow the normal custom and place the asteroids with the 

 ophiuroids ; instead she places her chapters in the order Holothuria, 

 Asteroidea, Echinoidea, Ophiuroidea. Her reasons for doing this 

 are stated on p. 699. In particular she decides that the ophiuroids 

 and the asteroids should be separated and the ophiuroids placed 

 withtheechinoidson the basis of larval development, the possession 

 of an epineural canal in the ophiuroids, and the possible occurrence 



