fXa '> •^' 



THE PROCESS OF ORIENTATION IN THE COLONIAL 



ORGANISM, GONIUM PECTORALE, AND A 



STUDY OF THE STRUCTURE AND 



FUNCTION OF THE EYE-SPOT 



S. O. MAST 

 From the Zoological Laboratory of the Johns Hopkins University 



SIX FIGURES 



CONTENTS 



1. Introduction 1 



2. Structure of Gonium 3 



3. Structure of the eye-spot in Gonium, Eudornia and other forms 5 



4. Process of orientation in Gonium 8 



5. Discussion 13 



6. Summary 16 



1. INTRODUCTION 



Among the most machine-like of the activities in organisms is 

 the process of orientation. It is consequently not surprising 

 that this process, which is common to so many different species, 

 has received much attent'on in the investigat'ons on behavior, 

 with the result that a mass of highly interesting and important 

 facts regarding it has been col ected. These facts seem to show 

 that the process of orientat on differs fundamentally in different 

 organisms and that it is far more comphcated than has been 

 assumed by some investigators, but that in general it facilitates 

 the life processes in the individuals possessing it, and conse- 

 quently tends to perpetuate the species. As to the reduction of 

 the process to mechanical principles even in its simplest form, 

 and as to its relation to conscious phenomena, little more can be 

 said than that the field here is still wide open, although prospects 

 are not altogether discouraging. 



Among the questions associated with the process of orienta- 

 tion concerning which there is at present much contention is 



1 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 20, NO. 1 

 JANUARY, 19l6 



