CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. 

 E. L. MARK, DIRECTOR. — No. 195. 



THE SENSORY REACTIONS OF AMPHIOXUS.i 



By G. H. Paekeb. 



Presented March 11, 1908. Received March 5, 1908. 



Table of Contents. 



Introduction 415 



Li^ht 416 



Heat 428 



Mechanical stimulation .... 431 



Chemical stimulation 436 



luterrehition of sensory meciian- 



isms in ampliioxus 439 



Central nervous system and sen- 

 sory mechanisms in ampliioxus 441 



Sensory meclianisms in amphioxus 

 and their relations to vertebrate 

 sense organs 443 



Summary 449 



Bibliography 450 



1. Introduction. 



Whatever position may be assigned to amphioxus in the classifi- 

 cation of the chordates, it is now generally admitted that this animal 

 retains many of the more primitive features of the ancestors of the 

 vertebrates. Such features not only occur in its anatomy and em- 

 bryology, but are to be expected in its activities. As the structure 

 of amphioxus throws light on the complex organization of the verte- 

 brates, so its activities, may give some indication of the way in which 

 the more complex functions of these animals have come into being. 

 It is from this standpoint that I have undertaken the study of the 

 sensory reactions of amphioxus. 



The material upon which this work was based is the so-called West 

 Indian amphioxus or lancelet, Branchiostoma caribbaeum Sundevall, a 

 close relative of the common European form, B. lanceolatum (Pallas). 

 This material was collected and studied during the summer of 1905 

 while I was at the laboratory of the Bermuda Biological Station 

 located at Hotel Frascati, Flatts Village, Bermuda. The living 



^ Contributions from the Bermuda Biological Station for Research, No. 12. 



