BIOCHEMICAL STUDIES OF PHYLOGENY 131 



sterols of the three crinoids thus far tested belong to Type I, al- 

 though perhaps a new variety, and those of holothurians classify as 

 Type II. Further biochemical evidence supporting the close re- 

 lationship of echinoids and ophiuroids concerns phosphagens or 

 phosphorus carriers, of great importance in metabolic processes." 

 Bergman (1949) gives the following table showing the various 

 species of echinoderms studied and the sterols present in each 

 (see Fig. 39). 



Asteroidea Stellasterol Hitodestrol Cholesterol 



Asterias rubens * 



Asterias forbesi * 



Asterias rollestoni * 



Asterias scoparius * 



Asterias pectinifera * 



Echinoidea 



Tripneustes esculentus 

 Centrechinus antillaram 

 Lytechinus variegatus 

 Heliocidenis crassidus 

 Arbacia punctulata 



Holothuria 

 Holothuria princepo * 



Cucumaria chronjhelmi * 



Ophiuroidea 

 Ophiopholis aculeata # ? 



From this table one can se e that the asteroids and the holothur- 

 ians both possess stellas te rol whilst the echinoids and possibly the 

 ophiuroids have cholesterol. This would link the asteroids and the 

 holothurians on the ne hand and the echinoids and ophiuroids 

 on the other hand, an arrangement which would agree with that 

 based on larval ch aracte ristics. 



Perhaps it will pay us to look at the steroid situation in a little 

 more detail. Bergman (1949) has given an interesting review of the 

 distribution of lipids in marine invertebrates with special refer- 

 ence to the sterols. At one time it was thought that cholesterol was 

 the only sterol present in these bodies but later work showed that 



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