MORPHOLOGY OF OTOCYSTS OF GONIONEMUS. 293 



interference with the functioning of that organ when only the 

 protective primary vesicle is collapsed. 



My observations upon specimens of G. rcrtcns and of G. mur- 

 bachii have failed to disclose any essential difference in the de- 

 tails of structure or in the general orientation of the otocysts of 

 these two species. 



RELATIONS OF OTOCYSTS TO BELL MARGIN. 



Because of the reliance placed upon the works of previous 

 investigators and writers on the subject, Mayer's "Medusae of 

 the World " includes several erroneous statements and incorrect 

 figures of the otocysts of Gonionemus. Few authors, with the 

 exception of Mayer, have attempted to describe definitely the 

 location of the otocysts with reference to their position on the 

 margin of the bell. It seems probable that his description is 

 based chiefly on Perkins' publication (1903: 786) which has been 

 extensively quoted by Mayer though his observations upon the 

 otocysts are very misleading. In Plate 34, Fig. 19, Perkins has 

 reproduced a drawing by Professor Brooks which shows the 

 otocysts as external projections, from the margin of the bell 

 between the bases of the tentacles. Further, the drawing of 

 the "radial transverse section" of the bell (Fig. 25 of his same 

 plate) confirms the impression of their external location. His 

 explanation of their origin is as follows : 



In the case of the sensory clubs, the endodermal tissue of the circular canal 

 grows down in a plug into the ectodermal tissue of the bell margin. This latter 

 becomes closely applied to the outside of the plug, as a thin investing epithe- 

 lium, and it also spreads out in a thin lamella over the inner surface of the 

 capsule which appears in the ectoderm of the developing club. 



Iii his summary Perkins (1903: 789) says, "sense organs appear 

 at determinate points on the bell margin." The work in this 

 article on sense organs seems to be principally that of Professor 

 W. K. Brooks whose observations were apparently accepted by 

 Perkins without attempt at verification. 



Mayer (1910: 341) in his synopsis of the genus seems to have 

 'ncorporated the foregoing incorrect observations bodily for he 

 Defers to the otocysts as " lithocysts external." On page 342 of 

 the same work he again states that there are " numerous ex- 



