Vol. XL. June, IQ2I. No. 6 



BIOLOGICAL BULLETIN 



MORPHOLOGY AND ORIENTATION OF THE 

 OTOCYSTS OF GONIONEMUS. 1 



L. J. THOMAS. 



INTRODUCTION. 



Gonionemus is used as an example of the Hydro-medusa in 

 many zoological laboratories of this country. In spite of this 

 fact relatively' little is known regarding the morphology and 

 orientation of the sense organs of the representatives of this 

 genus. Both the location and the structure of the otocysts have 

 been very imperfectly treated in the literature. Frequently 

 morphological and experimental treatises mentioning the otocysts 

 refer the reader to the works upon other genera, the otocysts of 

 which are presumed to be essentially similar to those of Gonio- 

 nemus. In studying specimens of Gonionemus vcrtcns Ag. and 

 of G. Jintrbachii Mayer the writer was impressed by the lack of 

 agreement between his direct observations and the published 

 statements by various early workers. These discrepancies led 

 the writer to investigate the problem further in an attempt to 

 discover the source of the statements which have been so gen- 

 erally incorporated into the literature and to determine, if pos- 

 sible, the precise structure and relationships of the otocysts in 

 this genus. 



On the Pacific coast of this country G. vcrtens A. Ag. occurs i'~> 

 the Puget Sound region and on the Atlantic coast G. uiurbachii 

 Mayer is found in abundance in the Eel Pond at Woods Hole, 

 Mass. Many references in the older literature incorrectly refer 

 to the Atlantic species as G. z f crtcns because at that time the 

 Atlantic form was not considered as specifically distinct from the 



i Contributions from the Zoological Laboratory of the University of Illinois, 

 No. 181. 



287 



