A STUDY OF SOCIALITY IN THE MADREPORARIA 
GERTRUDE VAN WAGENEN AND H. J. WEHMAN 
The type of sociality found in the Madreporaria is necessarily 
primitive. While we were making this study two criteria of 
sociality have been adopted and applied : first, the proximity of 
one corallite to another; second, organic communication between 
associated polyps and corallites. As the two criteria indicate, 
sociality is examined from the sandpoint of morphology of hard 
parts. This is necessary because of the extent of the field covered, 
the absence of live specimens, and the inclusion of fossils. 
The association in which there is no organic communication 
between the units may be called non-colonial ; the association in 
which there is organic continuation, colonial. The non-colonial 
associations include simple corals growing in the same locality, 
colonies flourishing on the same reef, and groups of larvae which, 
because of an especially favorable environment, have settled very 
near to each other. In the last-mentioned instance, should several 
of the larvae survive their hard parts would soon approach each 
other and coalesce, giving the appearance of a true colony. In 
such a case there is usually no communication between the ad- 
jacent visceral cavities; and the term pseudo-colonial is used. 
Other than this simple fusion of hard parts the non-colonial and 
pseudo-colonial associations are of no further interest morpho- 
logically. 
It is only reasonable to believe that the solitary corals preceded 
the colonial. The evidence of paleontology, while leaving some- 
thing to be desired, is definitely in favor of this view. The most 
ancient of all corals, the Archaeocyathidae, occur in the Cambrian. 
They are solitary, and no trace of a Cambrian colony has yet 
been found. The family Archaeocyathidae is considered to be- 
long to the Hexacoralla and Perforata, but for the most part the 
Paleozoic history of corals deals with the Tetracoralla. Of 
eleven genera of Ordovician Tetracoralla listed by Zittel (1913) 
only two were colonial (ten per cent) ; of twenty-eight genera from 
the Silurian nine were colonial (thirty-two per cent) ; of thirty- 
one genera from the Devonian eleven were colonial (thirty-five 
