132 BIOCHEMICAL STUDIES OF PHYLOGENY 



there were in fact over twenty different sterols, including optical 

 isomers, present in the invertebrates and that it is quite likely as 

 research proceeds that still more will be discovered. These 

 sterols differ in (1) the length of the side chain, (2) the presence or 

 absence of double bonds in this side chain, (3) the location of 

 double bonds in the main sterol skeleton. 



Up to 1949 the most studied phylum was the Porifera. This was 

 due to the fact that they were easily obtained in fairly large 

 quantities. Over fifty different species of sponges have been 

 analysed by Bergman and his colleagues and they have obtained 

 some very interesting results. In the first place they have dis- 

 covered more than ten different sterols in sponges, only two of 

 which had been known before. Secondly the presence or absence 

 of these sterols helped in the elucidation of certain systematic 

 problems. 



For some time a sponge from the Biscayne Bay, Florida, had 

 been given a variety of names. Some collectors had called it 

 Suberites distortus, others Suberites tuber culosus. Bergman (1949) 

 studied the sterols present in this sponge and showed that 

 clionasterol and poriferasterol were present. Now these sterols 

 were normally not found in the family Suberitidea but instead 

 were more often found in the Clionidae or the Choanatidea. 



Porifer- Neospongo- 

 sterol 



# 



Suberites was very carefully examined by Laubenfells, who 

 showed that there were some small microscleres present in the 

 tissues. These microscleres were diagnostic of the genus 

 Anthosigmelia, which is in the family Choanitidea. This then would 

 mean that the sponge was not a Suberitidae but a Choanitidae and 

 this would agree with the sterol assay. 



A more complex case is present in that of Hymeniacidon 

 heliophila. This sponge has been described both as Hymeniacidon 

 heliophila and as Stylotella heliophila. The genus Stylotella is 



