BROWN, RUGOSE CORALS 
49 
pair as suggested by the earlier writers, but that the counter quadrants were 
accelerated in development over the cardinal quadrants and that the first 
pair of secondary septa appeared in the counter quadrants very early. 
In the present paper, it is proposed to study a few of the rugose corals 
included in the Zaphrentid group both geologically in the order of their 
occurrence and phylogenetically in the order and mode of their development 
and to find, if possible, some natural order in which to group these forms 
systematically. 
Although the Zaphrentid corals have been known for a long time, and 
although the representatives are very numerous and abundant and occur 
throughout the geological formations from early Ordovicic to the end of the 
Carbonic, few attempts have yet been made to trace out the ontogeny and 
phylogeny of their numerous genera and species. 
In recent work in paleontology, certain principles and laws have come 
to be recognized as universal in their application. If these laws are applied 
in a study of the development and relationship of the genera and species of 
the family Zaphrentidse, new and heretofore unsuspected truths are brought 
to light. Some of the apparently widely separated species of this more or 
less heterogeneous group are found to be very closely related, and some of 
the species which at first sight are very closely related really prove to be 
widely separated when arranged in their true relationship. 
Among the most important of the principles of development which must 
be kept in mind when studying the phylogeny or race history of any group 
of living forms are these three first announced by Alpheus Hyatt. 1 
Stages in Individual Development. In the young, stages are found 
the equivalents of which are to be sought in the adults of ancestral types. 
Acceleration in Development. “All modifications and variations in pro¬ 
gressive series tend to appear first in the adolescent or adult stages of growth, 
and then tend to be inherited in successive descendants at earlier and earlier 
stages according to the law of acceleration, until they either become embry¬ 
onic, or are crowded out of the organization, and replaced in the development 
by characteristics of later origin.” 
Morphological Equivalence. “In the different genetic series of a type 
derived from one ancestral stock, there is a perpetual recurrence of similar 
forms in similar succession, which are usually called representative and often 
falsely classified together, though they really belong to divergent, genetic 
series.” 
If these important principles of development are kept in mind and it is 
1 "Genesis of the Arietidse,” Smithsonian Contributions to Knowledge, 673, 1SS9. 
