BOTRYLLUS SCHLOSSERI (PALLAS): THE 



BEHAVIOR OF THE LARVA WITH 



SPECIAL REFERENCE TO THE 



HABITAT. 1 



HELEN WOODBRIUGE, 

 UNIVERSITY OF MAINE. 



The purpose of the work reported in this paper was to deter- 

 mine more accurately than had been possible previously, the nature 

 and effect of certain of the responses of the larva of Botryllus, 

 and to investigate more fully the relation they bear to the ap- 

 parent " selection " on the part of the larva of the place for attach- 

 ment preparatory to metamorphosis. The work was done during 

 the summer of 1923, at the Marine Biological Laboratory, Woods 

 Hole, Massachusetts. 



Thanks are due to the university of Maine for making the work 

 possible, to the Marine Biological Laboratory for the facilities 

 for the work, and in large measure to Dr. Caswell Grave for his 

 helpful suggestions and generous assistance. 



During the course of previous experiments, some evidence 

 appeared indicating that the Botryllus larva tends to '" select " 

 definite places of attachment for metamorphosis. Larvse were al- 

 lowed to undergo metamorphosis in crystallization dishes contain- 

 ing blades of eel grass stretched obliquely from the bottom of one 

 side of the dish to the top of the other, and held in place by glass 

 slides. When sufficient time had elapsed for metamorphosis to 

 take place, the location of the zooids was noted. Measurements 

 of the eel grass, the diameter of the dishes, and the depth of water 

 were made in each case, and calculations were made to determine 

 the total area available to the larvae for metamorphosis, and the 

 percent of that area which was offered by the eel grass. Similar- 

 ly, the percentage of larvae metamorphosing on the eel grass was 



i This paper is supplementary to one previously written by Dr. Grave and 

 myself on the same species of Botryllus. It may be found in the Journal of 

 Morphology, Volume 39, Number i. 



223 



