490 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



The two should not be at loggerheads in this way, and need not be, 

 if the data are handled in the way here advocated. 



If the postlarval stages alone are a guide to phylogeny in echino- 

 derms, as I have always believed and advocated, the entire picture 

 returns to its focus, and acquires once more that definition which it 

 lost when larval embryology took control after 1900. The clarity of 

 the picture enables predictions to be made and, as now twice demon- 

 strated, the predictions can be tested and confirmed. 



It is now evident that the conventional classification into Eleu- 

 therozoa of all free-living echinoderms is inadequate. The assemblage 

 is made up of two quite different stocks, of different age and different 

 derivation, and to maintain Eleutherozoa as a formal unit of classi- 

 fication will merely conceal the true relationship between included 



and excluded classes. 



PHYLOGENY 



Although the details are not quite finalized, figure 18 indicates the 

 general proposals which now seem reasonable. It is proposed to 

 replace the old subphylum Eleutherozoa by two new subphyla, the 

 Asterozoa and Echinozoa, whose content is illustrated in the diagram. 

 Their inferred relationships are approximately indicated on the dia- 

 gram, in which, of course, the time scale is necessarily distorted. No 

 such proposals can possibly be definitive, and we may be sure that 

 many modifications will become necessary with new discoveries. I am 

 confident, however, that by abandoning the Eleutherozoa as a unit, 

 and by transferring the stress to dynamic processes governing the 

 growth of postlarval stages, the way will be opened to a more fruitful 

 line of investigation in future. As for the larval stages themselves, 

 surely they can only be secondary, late-evolved stages of development, 

 specially adapted to meet temporary conditions in a planktonic phase 

 of development, so that they are examples of "clandestine" evolu- 

 tion, giving no direct indication of the structure or the habit of the 

 ancestral stocks from which echinoderms descend. 



REFERENCES 

 (Note: References prior to 1962 are given in the first item below.) 



Fell H. Barraclouqh. 



In press. Phylogeny of sea-stars. Phil. Trans., ser. B. 



1962a. Science, vol. 136, pp. 6.33-G36. 



1962b. Univ. Kansas Paleont. Contr., Echinodermata : vol. 6. 



1962c. Zool. Zhurn. Akad. Nauk. S.S.S.R., vol. 41, No. 9. 



1962d. Publ. Seto Marine Biol. Lab., vol. 10, No. 2. 



1962e. Tuatara, Journ. Biol. Soc. Victoria Univ., Wellington, vol. 10, 



No. 3, pp. 138-140. 

 1962f. Native sea-stars of New Zealand (A. H. and A. W. Reed). 



