AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, JULY 12 
ACTIVITIES OF COLONIAL ANIMALS 
I. CIRCULATION OF WATER IN RENILLA! 
G. H. PARKER 
ONE TEXT FIGURE AND ONE PLATE (FOUR FIGURES) 
INTRODUCTION 
Although much attention has been devoted in the last few dec- 
ades to the movements, reactions, and other activities of single 
individual animals among the coelenterates, such, for instance, 
as the sea-anemones and the Jjelly-fishes, very little effort has 
been directed toward the study of colonial forms, like the corals 
and the hydroids. At present it is quite impossible to state with 
any degree of certainty how, from the standpoint of functional 
interdependence, the individual zoéids in such a colony are related 
to the colony as a whole. For the solution of a question of this 
kind a well-circumscribed aggregate of large zodids is needed. 
Such a condition is to be met with in the sea-pen, Renilla. The 
zooids in this genus are relatively large, and the whole colony, 
though anchored in the sand, can be removed without damage 
and readily subjected to experimental study. 
This genus, though restricted to the warmer seas, is distributed 
very widely within such limits. One of its largest species is 
Renilla amethystina Verrill, a form very abundant in the shallow 
waters about San Diego, California. This species was chosen 
for experimental investigation, and all the material used in this 
work was collected near the outlet of False Bay in the vicinity of 
La Jolla, California. JI am under obligations to Dr. W. E. Ritter, 
Director of the Scripps Institution for Biological Research at La 
Jolla, for the opportunity of carrying out this work, and I am 
indebted to the staff of that institution, especially to the collector, 
' Contributions from the Zoélogical Laboratory of the Museum of Comparative 
Zodlogy at Harvard College, no. 323. 
343 
