No. 6.] AMERICAN MORPHOLOGICAL SOCIETY. 359 



end of the summer, do reproduce asexually to a considerable 

 extent. Later this ceases and the reproductive organs develop. 

 These statements are based upon observations extending over 

 from two to three years. 



A possible explanation is that the asexual reproduction may 

 be substituted for the sexual in certain localities during con- 

 siderable periods, but further data are necessary to confirm 

 this. 



XXIII. VARIATION AMONG HYDROMEDUSAE. 



CHARLES W. HARGITT. 



OBSERVATIONS upon variations among the Hydromedusae 

 seem to have been of comparatively limited extent. Refer- 

 ences to the subject are to be found in the writings of Ehren- 

 berg, Forbes, Agassiz, Hincks, Romanes, and later by Agassiz 

 and Woodworth, but except in the last-named paper they are 

 rather incidental and fragmentary. 



Of my own observations only the barest abstract and sum- 

 mary can be undertaken in this connection. 



Among the genera studied the principal have been as 

 follows : Pennaria, Encopc, Obelia, Margclis, Gonionemns, 

 NemopsiSy, Rkegmatodes. 



The principal organs examined were: (i) The Chymiferous 

 Canals, (2) Tentacles, (3) Gonads, (4) Otocysts. Among these 

 the greatest range of variation was noted in the tentacles, as 

 might naturally be expected, in some cases reaching as high as 

 90 per cent. In the forking and doubling of tentacles there 

 was least, rarely exceeding 5 per cent, and indeed seldom 

 reaching that ratio ; in Gonionemus 3 per cent. 



In the looping, branching, and anastomosing of chymiferous 

 canals there was great variation in different genera, in some 

 being almost nil, while in others (Encope and Gonionemus) 

 varying from 5 to 10 per cent. 



Considerable variation was found in the gonads, though less 

 than in the other organs already noted, varying in different 

 genera from 2 to 5 per cent. While considerable variation 



