48 
ANNALS NEW YORK ACADEMY OF SCIENCES 
Until Duerden took up the question, only adult corallites or the young 
tips had been studied, the attention of paleontologists being confined to the 
full-grown or very young individuals. Little or no attention was devoted 
to the method of growth and development of the individual. While working 
upon the growth and development of the embryos of modern corals, Duerden 
turned his attention to the developmental stages preserved in fossil corals. 
He attempted to harmonize the young stages of these rugose corals with the 
methods of growth and development which he found in modern forms 
and cut serial sections to show the successive stages of morphological devel¬ 
opment of the individuals. As a species to study, he selected Lophophyllum 
proliferum from the Carbonic limestones, because specimens were both 
plentiful and well-preserved. By making thin microscopic sections trans¬ 
verse to the tip of the corallites, he obtained stages in development which he 
considered identical with those found in the early embryonic stages of 
hexamerous forms. 1 
In February 1906, Gordon questioned Duerden’s interpretation. 2 He 
showed how Duerden’s observations could easily be explained by an accelera¬ 
tion of certain septa on the basis of an original tetrameral condition, and 
from his own studies of young silicified specimens of Streptelasma profundum 
from the Trenton and Black River limestones showed that in the youngest 
stages of these geologically early forms only four primary septa occurred. 
Duerden replied to this, 3 and stated that in six distinct species of rugose 
corals, Streptelasma rectum Hall, Cyathaxonia cynodon E. & H., Hadro- 
phyllum glans (White), H. pauciradiatum E. & H., Microcyclus discus 
Meek and Worthen and Lophophyllum proliferum E. & H., he had found 
the earliest stages obtainable to have six primary septa, and therefore he 
considered that all rugose corals were derived from original hexamerous 
forms and that the four-fold condition was of secondary derivation. 
In the American Journal of Science for April, 1907, the author showed 
that of these six species studied by Duerden, four were Devonic forms and 
the other two Carbonic in age. All of them, therefore, occurred very late 
in the geological distribution of the Rugosa. Of the four Devonic forms, 
three were almost disc-like and therefore were highly specialized and pre¬ 
sented extreme difficulties, when one attempted to get at the earliest stages 
of growth. In case of the fourth form, Streptelasma rectum, Hall, he showed 
that a quadriseptate stage, earlier than any observed by Duerden, could be 
found in very perfect material, and that the secondary septa came in pair by 
1 Johns Hopkins University Circular, Jan., 1902; Annals & Magazine of Natural History. 
May, 1902. 
2 American Journal of Science, Vol. XXI, pp. 109-127, Feb., 1906. 
3 Science, Aug. 24, 1906; Annals & Magazine of Natural History, Sept., 1906. 
