Published online by Cambridge University Press: 01 May 2009
A reinterpretation is attempted of the 25 years of graptolite ultrastructural work based upon the present state of knowledge. It is emphasized that studies need to embrace many more species of graptolites, particularly in the dichograptid groups, and with different growth stages, before the gross evolution of ultrastructural elements can be satisfactorily appraised. The factual (morphological, ultrastructural) data are themselves reappraised, summarized, and very tentatively related to Bulman's anagenetic grades of graptolite development.